Although countless variants of poker are described in the literature of the game, they all share certain essential features. A poker hand comprises five cards. The value of the hand is in inverse proportion to its mathematical frequency; that is, the more unusual the combination of cards, the higher the hand ranks. Each player may bet that he has the best hand, and other players must either call his bet or concede. A player may bluff by betting he has the best hand when in fact he does not, and he may win by bluffing if players holding superior hands do not call his bet.

There are forms of poker suitable to any number of players from 2 to 14, but in most forms the ideal number is 6, 7, or 8 players. The object is to win the “pot,” which is the aggregate of all bets made by all players in any one deal. The pot may be won either by having the highest-ranking poker hand or by making a bet that no other player calls. The following principles apply to nearly all forms of poker.

Poker is almost always played with the standard 52-card deck, the playing cards (playing card) in each of the four suits (spades, hearts, diamonds, clubs) ranking A (high), K, Q, J, 10, 9, 8, 7, 6, 5, 4, 3, 2, A (low only in the straight or straight flush 5-4-3-2-A and in certain variants described below).

In social play, especially in “dealer's choice,” certain cards may be designated wild cards. A wild card stands for any other card its holder wishes to name. There are many methods of introducing wild cards into the game. The most popular are:

At the start of the game, any player takes a pack of cards and deals them in rotation to the left, one at a time faceup, until a jack appears; the player receiving that card becomes the first dealer. The turn to deal and the turn to bet always pass to the left from player to player. For each deal any player may shuffle the cards, the dealer having the last right to shuffle. The dealer must offer the shuffled pack to the opponent to the right for a cut. If that player declines to cut, any other player may cut.

A professional dealer is used in poker clubs, casinos, and tournament play, where a round disc (known as a dealer button) is passed clockwise each hand to indicate the nominal dealer for betting purposes. Also, such environments almost invariably charge the players either by setting an hourly rental fee for their seats or by “raking” a small percentage (say, 5 percent) from each pot.

In each deal there are one or more betting intervals according to the specific poker variant. In each betting interval one player, as designated by the rules of the variant being played, has the privilege or obligation of making the first bet. This player and each player in turn after him must place in the pot the number of chips (representing money, for which poker is almost invariably played) to make his total contribution to the pot at least equal to the total contribution of the player before him. When a player does this, he is said to be in the pot, or an active player. If a player declines to do this, he discards his hand and is said to drop or fold, and he may no longer compete for the pot.

Before the deal each player may be required to make a contribution to the pot, called an ante. In each betting interval the first player to make a bet is said to bet, a player who exactly meets the previous bet is said to call, and a player who bets more than the previous bettor is said to raise. In some variants a player is permitted to check, which is to stay in without betting, provided no other player has made a bet in that betting interval. Since a player cannot raise his own bet, each betting interval ends when the betting turn has returned to the person who made the last raise or when all players have checked.

At the end of each betting interval except the last, dealing is resumed; at the end of the last betting interval, there is the “showdown,” in which each active player shows his full hand, and the highest-ranking hand wins the pot.

In poker legends there are “no-limit” or “sky's-the-limit” games, but in practice some limit is placed on what one may bet in any game. There are three popular methods.

No one may bet or raise by more than the established limit. In draw poker the limit is usually twice as much after the draw as before—for example, two chips before the draw, four chips after. In stud poker the limit is usually twice as much in the final betting interval as in previous betting intervals. (The higher limit applies also when any player's exposed cards include a pair.) These respective forms of the game are described below. In a fixed-limit game a limit is usually placed on the number of raises that may be made in any betting interval.

A player may bet or raise by no more than the amount in the pot at the time the bet or raise is made. When raising, the player may first put in the pot the number of chips required to call the previous bet and then raise by the number of chips in the pot. When pot limit is played, it is customary also to place a maximum limit on any bet or raise, regardless of the size of the pot.

This method most closely approximates the legendary no-limit game. Each player's limit is the number of chips he has on the table at the beginning of the deal. He may not bet more, but for this amount he may call any higher bet (go “all in”) and compete for the pot in the showdown. Other players having more chips may continue to bet, but their further bets go into one or more side pots in the manner decided among the players who contributed fully to the side pot. When a player drops out of any side pot, he drops out of the original pot as well, in effect surrendering his rights in the original pot to the player whose later bet he did not call. Thus, there may be different winners of the main pot and various side pots.

Poker has three main branches. In draw poker each player's full hand remains concealed until the showdown; in stud poker some but not all of a player's cards are dealt faceup; and in community-card poker some cards are exposed and used by all the players to form their best hands. In addition, nearly any form of poker may be played high-low (also spelled hi-lo) or low (also known as lowball). In high-low the highest-ranking poker hand and the lowest-ranking poker hand divide the pot equally. If there is an odd chip, the high hand gets it. If two or more hands tie for high or low, they divide their half of the pot equally. In most games the lowest possible hand is 7-5-4-3-2 in two or more suits, but in some games the ace may optionally be treated as the lowest card and thereby make 6-4-3-2-A the lowest hand and a pair of aces the lowest pair.

In straight poker each player is dealt five cards facedown, and the deal is followed by one betting interval, beginning with the player nearest the dealer's left, and then a showdown. It quickly was eclipsed by draw poker, which allows each active player, in turn beginning at dealer's left, to discard one or more of his original cards and receive replacements for them from the undealt portion of the pack. (A player who declines to draw cards is said to “stand pat.”) After this process, called the draw, there is a second betting interval, followed by the showdown. Sometimes a minimum hand, such as a pair of jacks, is required in order to make the first bet before the draw.

Draw poker declined in popularity during the second half of the 20th century in favour of stud poker and, especially, various community-card poker games.

Each player receives one card facedown—his hole card—and one card faceup. The deal is then interrupted for a betting interval. There follow three rounds of dealing, each deal distributing one card faceup to each active player, with a betting interval after each round. There is a showdown in which the hole cards are shown after the fourth and last betting interval. In each betting interval the first bettor is the player with the highest-ranking poker combination in his faceup cards; if two or more players have the same combinations, the “first” one (nearest the dealer's left) bets first. In the first betting interval the first player must bet at least an established minimum; in any later betting interval he may check.

Few games have lost popularity so fast as regular five-card stud. In the 1920s and into the '30s, it was played in two-thirds of the high-stakes and professional games in the United States; since the 1950s it has not been played in even one-tenth of them.

Each player is dealt two hole cards and a faceup card, and there is a betting interval. Then three more faceup cards and one final facedown card are dealt to each player, each of these four deals being followed by another betting interval. For the showdown each player selects the best five of his seven cards to be his poker hand.

There are six-card and eight-card variants of this game, in each of which a player ultimately selects five of his cards. Seven-card stud is often played high-low or low. In some high-low games, players may vie for both halves of the pot by selecting any five of their cards as a candidate for high hand and any five as a candidate for low hand. In some high-low games, declarations are required: before the showdown each player must announce whether he is trying for high, for low, or for both, and he cannot win unless his entire announcement is fulfilled.

Unlike five-card stud, seven-card stud remains one of the most popular poker variants in homes, poker clubs, and poker tournaments. In particular, the game favours players adept at adjusting their calculations on the basis of the numerous exposed cards.

The most popular game of the modern era is Texas hold'em, which world champion poker player Doyle (“Texas Dolly”) Brunson once called the “Cadillac of poker games.” This is a studlike game in which players share five cards (community cards) dealt faceup on the table in order to form their best hands. The game is usually played with a fixed limit or pot limit in home and casino play. However, Texas hold'em tournaments almost always use table stakes (hence the often-heard expression “all in”) in order to determine the winner more quickly by a process of elimination.

Rather than a traditional ante from each player before the deal, in Texas hold'em only two players are forced to bet blind before seeing their cards. The position to the dealer's left is called the small blind because the player in that seat must make a small bet (typically one-half the minimum bet), and the position to the left of the small blind is called the big blind because that player must raise by placing twice as many chips in the pot. Every player is then dealt two cards facedown, and the player to the left of the big blind is the first to act (fold, call the big blind, or raise); if no player raises the big blind, the big blind may check or raise his own bet to continue the betting. Next the dealer “burns” one card from the top of the deck (deals it facedown to the table) and then deals the first three community cards (the “flop”) faceup to the table. The small blind (or the player to his left still in the hand) acts first in this and every succeeding round by folding, checking, or making a bet. After all bets have been called or every active player has checked, another card is burned, and a fourth common card (called “fourth street” or “the turn”) is dealt faceup. There is another round of betting. Then another card is burned, and the fifth common card (called “fifth street” or “the river”) is dealt faceup, followed by the last round of betting. Each remaining player then makes his best hand from the shared community cards and his two hole cards to determine the winner.

The play and betting in Omaha are similar to Texas hold'em. However, instead of two hole cards, Omaha players are dealt four hole cards to start the betting. Then there is a flop of three community cards before the last round of betting. Furthermore, players must use only two of their hole cards and all three community cards to make their hands. Omaha is often played lowball. Because flushes and straights are not counted in Omaha lowball games, the best hand is A-2-3-4-5, suits not being considered. There is also a game called Omaha high-low split pot. With two pots there are two winners, one having the best high hand and the other the best low hand. Omaha games are quite popular and are played in the World Series of Poker (poker), described below.

In informal poker games, each successive dealer is usually permitted to dictate the variant of poker that will be played. This privilege is most often expressed by the dealer selecting one of the forms of poker described above. The dealer may also designate certain cards to be wild or certain nonstandard hands to be counted, such as “big tiger” (king high, 8 low, no pair), “little tiger” (8 high, 3 low, no pair), “big dog” (ace high, 9 low, no pair), and “little dog” (7 high, 2 low, no pair), which rank in the given order and beat any straight but lose to any flush; “blaze” (five face cards), which beats two pairs and loses to three of a kind; and “four flush” (four cards in one suit), which beats one pair and loses to two pairs. Sometimes it is agreed that the dealer can select or invent any variant he wishes, subject to only two restrictions: the dealer cannot require any player to ante more than any other player; and if the game requires a minimum to open and is passed out, the same dealer deals again.

Poker-type games have also been developed to allow a player to make wagers against a casino. Winnings may be given if the player has a better hand than a casino dealer, or they may be given to players who have specific hands.

Video poker games have very little appeal to serious poker players because the human element is completely removed from the contest—which thus eliminates bluffing and tells (“reading” other players) as well as most betting strategies. However, such machines have become the most popular slot machines in most casinos. Also, several state lotteries use video poker lottery terminals. Typically, a player is dealt a five-card hand on the face of a video screen and is allowed to ask for one or more new cards as in draw poker. The player may be awarded various winnings according to the value of the final hand.

In Caribbean stud poker each player pits a five-card stud hand against the dealer's hand. First the players make an ante bet. Then the dealer gives the players and himself five cards each. Four of the dealer's cards are dealt facedown and one faceup. The players look at their cards and then either fold or bet an amount double their ante. After the players have finished betting, the dealer looks at his cards to determine if he has a “qualifying hand.” A qualifying hand is ace-king high or better. If the dealer's hand does not qualify, the dealer folds and pays each remaining player the amount of the ante; the second bets are ignored.

However, if the dealer's hand does qualify, each player either loses (if the dealer has the better hand) or wins an amount equal to the ante plus an amount on the second bet according to the following schedule: ace-king high or one pair, 1 to 1; two pair, 2 to 1; three of a kind, 3 to 1; straight, 4 to 1; flush, 5 to 1; full house, 7 to 1; four of a kind, 20 to 1; straight flush, 50 to 1; and royal flush, 100 to 1.

There is another side bet that the player may make at the beginning. The player may bet $1 on the value of his hand and can win a special payoff for staying in the betting, even if the dealer's hand does not qualify. The casino will have a progressive jackpot for this bet. A flush will get $50, a full house $100, a straight flush 10 percent of the progressive jackpot, and a royal flush the full jackpot. The jackpot keeps growing until there is a winner.

Let it ride is a five-card stud poker game. There is no dealer's hand in this house-banked game. Each player lays three equal bets on the table before receiving three cards facedown. Then each player may let his first bet stay on the table, or he may withdraw it. A community card is then dealt faceup, and each player decides whether to withdraw his second bet or “let it ride.” His third bet must stay. Then a final community card is revealed. Each player now has a five-card poker hand, which is paid off according to a schedule. If a player does not have at least a pair of 10s, he loses any bets that he did not withdraw. A pair of 10s gets the bettor's wagers returned to him. Two pairs give him a return of 2 to 1 on bets that he let ride; three of a kind, 3 to 1; a straight, 5 to 1; a flush, 8 to 1; a full house, 11 to 1; four of a kind, 50 to 1; a straight flush, 200 to 1; and a royal flush, 1,000 to 1. Like Caribbean stud, there is also an opportunity to make a $1 bonus bet that pays off 20,000 to 1 for a royal flush and less for other good hands.

Pai-gow poker is a house-banked even-payout game. Each player is given seven cards, as is the dealer. Each then makes his best two-card and best five-card hand. If both of a player's hands are better than the dealer's two hands, the player wins an amount equal to his bet, less a 5 percent commission on the winnings. If both of the dealer's hands are better, the dealer wins the wager. Otherwise, the player takes back his bet. A standard 52-card deck is used along with a joker, which may be used as an ace or to complete a straight or a flush. The best possible hand is five aces.

Three-card poker is a house-banked stud game in which three cards are dealt facedown to each player and the dealer. Each player makes two initial bets, one bet placed on a centre circle and the other placed on an ante square. The centre circle bet can be won if the player's three cards show certain values—e.g., the player wins 2 to 1 for a pair or 5 to 1 for a three-card straight. The ante bet places the player's hand against the dealer's hand. After the deal the player may choose to drop out by forfeiting the ante or stay by raising. If the dealer does not have an opening, or qualifying, hand (queen high or better), the dealer pays the player 2 to 1 for the ante bet, and the raise is canceled. If the dealer can open, then both the ante and the raise are wagered against the dealer, who either wins both or pays the player 2 to 1 for both. A bonus square may also permit the player to wager for a payoff on a “super” hand, such as three of a kind or a three-card straight flush.

Poker rewards skillful play better than any other card game. Though it is not so complex a game as bridge, the player has greater control over the result (largely because the player is permitted to drop bad hands); consequently, a good player is less likely to lose in a game with inferior players.

From a practical standpoint, the player chiefly needs to know what constitutes a good hand, a fair hand, and a poor hand in a given form of poker. The fundamental principle of skillful play is that a person should generally stay in the pot only if he probably has the best hand or if the odds against his drawing the best hand are less than the odds offered by the pot. To illustrate the latter: There are four chips in the pot, and the player must put in one chip to stay; therefore, the pot offers odds of 4 to 1. The player has a four flush or a “bobtail” straight (open at both ends, as 8-7-6-5), from either of which he can draw one card. The odds against filling either of these hands are almost 5 to 1. The pot offers less than the odds against filling, so the player should fold.

Beyond the mathematical odds for holding or improving different hands, observation plays a significant role. In particular, body language often gives away whether a player is bluffing or has the “nuts” (an unbeatable hand). Such tell signs, or “tells,” include a player's breathing patterns, facial expressions, hand movements, and manner and content of speech. In general, inexperienced players tend to act contrary to their hands—trying to appear bold to scare off calls when they bluff and meek (or suddenly quiet) with a strong hand in the hope that other players will call or raise.

In addition to disguising one's emotions—affecting the proverbial “poker face”—good players will adjust their style of play according to the style of their opponents. In typical casual games with low betting limits, too many people play weak hands out rather than fold; in such “loose” games, it pays to play “tight,” since bluffing will seldom work. However, a tight player who never bluffs, even in loose games, will lose opportunities for bigger pots because his reputation will limit the action he can get when he does get a strong hand. For this reason good players may try to convince the other players that they play loose and often bluff, even at the expense of losing a few (small) pots when they are called with weak hands.

The principle of poker is very ancient. One of its ancestral games—primero (Spain), primiera (Italy), la prime (France)—appears in literature at least as early as 1526. In this game each player had three cards, and the counting combinations were three of a kind, a pair, and a flux (flush; three cards of the same suit). In later developments certain cards had special value, equivalent to wild cards in modern poker. By about 1700 the betting and bluffing aspects had produced the games of brag in England (one of four card games about which Edmond Hoyle (Hoyle, Edmond) wrote) and pochen (its name meaning “to bluff”) in Germany. From the latter the French developed a similar game called poque, first played in French America in 1803, when the Louisiana Purchase made New Orleans and its environs territories of the United States. During the next 20 years, English-speaking settlers in the Louisiana Territory adopted the game, Anglicized its name to poker, and established the essential features of the modern game.

The earliest known reference to poker in American literature occurs in the memoirs (1829) of Joe Cowell, a touring English actor. From his description it is clear that the original American game was played with a pack of cards that included five cards for each player; all the cards were dealt, and the players bet on who had the best five-card combination. So played, poker is virtually indistinguishable from an older Persian game called as nas, a four-hand game played with a 20-card pack, five cards dealt to each player. This coincidence led some students of games to call poker a derivative of as nas, but this theory has been discredited.

By 1834, the date of the second known reference to poker, the game had been adapted to the modern 52-card deck. No description of poker is given in any book of the rules of games before 1858, but, in such books published in the 1860s, it is not characterized as a new game. The history of the game since then consists entirely of new features introduced to encourage freer betting: the straight, introduced as an additional valuable hand; the draw, so that players might stay in even when not originally dealt good hands; stud poker, to increase the number of opportunities for betting; and the jackpots, originally applying only to a pot to which each player antes, creating an unusually large pot at the start. Most of the innovations came in the decade 1861–70 and probably were engendered in the great amount of poker played by soldiers on both sides in the Civil War. Poker was a favourite in saloons throughout the American “Wild West” during the 1870s and '80s, and, contrary to Hollywood movies, the games rarely led to shoot-outs over accusations of cheating.

The spread of poker to other countries probably began in 1871, when Colonel Jacob Schenck, the U.S. minister to Great Britain, explained the game to a group of gentlemen that included members of the British court. Queen Victoria heard about the game and expressed interest, whereupon Schenck wrote and had privately printed (1872) a set of rules to send to her. This is the earliest known work devoted exclusively to poker, although the game had previously been treated in compendiums. Poker was already sufficiently identified with the United States so that Schenck described it as “our national game.” However, this may have been only because all other card games played in the United States were undeniably of European (Europe) origin. Although poker had a brief vogue in British court circles in the 1870s, its widespread acceptance in Great Britain and on the Continent came chiefly in the decade 1911–20 and was undoubtedly much influenced by the American Expeditionary Force in World War I.

For nearly 100 years in the United States, poker was considered a gambling game of men—unsuited to polite or mixed gatherings—but after the 1920s its popularity extended to both sexes and all levels of society. Surveys conducted in the middle of the 20th century showed poker to be the favourite card game of American men and the third most-favoured (after rummy and bridge) of American women, and in Great Britain it ranked next after contract bridge with both sexes.

The idea of a big game with the best players remained in Binion's mind for two decades. Then, a year after celebrating a reunion of Texas poker players in Reno, he decided to invite the best players to Las Vegas for what he called the World Series of Poker. The initial game in 1970 involved six players who each paid a $5,000 entry fee. Two years later the fee was $10,000, and it was agreed that play would continue until all players had gone “all in” and only one player remained at the table. Johnny Moss won three of the first four tournaments. Slowly the tournament grew as more people were invited to play and anyone could put forth $10,000 and sit with the best poker players in the world. Soon the tournament was split several ways, with contests for the surviving player in seven-card stud, Omaha, high-low stud, and Texas hold'em games and later with special restricted tournaments for seniors and for women. The winner of each event gets an engraved gold bracelet in addition to the prize money. The Texas hold'em game is the most prestigious, with its winner considered the poker world champion. Among early winners were Doyle (“Texas Dolly”) Brunson, Johnny Chan, Thomas (“Amarillo Slim”) Preston, and Stu Ungar.

Many satellite tournaments have been spawned by the WSOP, and their winners are given the entry fee to the Horseshoe games. Entry fees for the satellites can be as low as $10. Some card-room casinos use satellites as publicity draws and occasionally waive the fee. Satellites are accessible to people everywhere, especially as multiple tournaments are held over the Internet.

The WSOP has also been the inspiration for many other large tournaments—in particular, the World Poker Tour. Presented in weekly episodes on a cable television network, the World Poker Tour began in 2003 and consists of a dozen main events. It also conducts satellite tournaments and sponsors games on the Internet.

Poker games are available on hundreds of Internet sites, offering play 24 hours a day, seven days a week, for dozens of poker variants. “Ring” games are ongoing games in which players join the action at any time by purchasing chips, play as long as desired, and are free to leave anytime with their remaining chips. In “on demand” poker tournaments, players choose the poker variant and betting limit, and play begins when enough players (typically 9 or 10) have signed up to complete a table. Players bring a set amount of money to the table, and play continues until only one player survives. For scheduled tournaments players sign up to play for a set amount of prize money. They must pay a “buy-in” fee, and they each receive the same number of chips for play. They play until there is a single winner. These tournaments are common as satellites for large tournaments such as the WSOP.

Poker sites on the Internet are hosted by offshore operators. The U.S. 1961 Wire Act has been interpreted by enforcement authorities, as well as by U.S. courts, as prohibiting gambling through the Internet by patrons in the United States. Foreign Internet betting companies, mostly located in small Caribbean countries, do market to American customers, and authorities find it difficult to stop the practice. However, they have seized operators who have physically gone to the United States. But this matter is far from clear. There are claims, for example, that the Wire Act applies only to sports betting and only to betting over telephone lines. Moreover, an appellate body of the World Trade Organization (WTO) ruled in 2004 that Internet operations in Antigua could serve American customers because the United States permits Internet betting for horse races through the Interstate Horseracing Act (IHA) of 1978. U.S. authorities disputed the ruling and sought a review and rehearing of the matter. In 2005 the WTO upheld the gist of its original ruling, including an order that the IHA be amended to no longer discriminate against foreign Internet gambling services, and threatened to impose trade sanctions under the General Agreement on Tariffs and Trade (GATT) unless the United States complied with its orders by April 3, 2006. The deadline passed with the U.S. government insisting on the right to ban Internet gambling. Various U.S. states have also passed laws against gambling over the Internet, including playing poker for money.