Most geckos have feet modified for climbing. The pads of their long toes are covered with small plates that are in turn covered with numerous tiny, hairlike processes that are forked at the end. These microscopic hooks cling to small surface irregularities, enabling geckos to climb smooth and vertical surfaces and even to run across smooth ceilings. Some geckos also have retractable claws. Like snakes (snake), most geckos have a clear protective covering over the eyes. The pupils of common nocturnal species are vertical and are often lobed in such a manner that they close to form four pinpoints. The tails of geckos may be long and tapering, short and blunt, or even globular. The tail serves in many species as an energy storehouse on which the animal can draw during unfavourable conditions. The tail may also be extremely fragile and if detached is quickly regenerated in its original shape. Geckos' colours are usually drab, with grays, browns, and dirty whites predominating, though Phelsuma, a genus made up of the day geckos of Madagascar, is bright green and active in the daytime. Unlike other reptiles, most geckos have a voice, the call differing with the species and ranging from a feeble click or chirp to a shrill cackle or bark . Most species are oviparous (oviparity), the eggs being white and hard-shelled and usually laid beneath the bark of trees or attached to the underside of leaves. A few species in New Zealand give birth to live young.

Geckos are abundant throughout the warm areas of the world, and at least a few species occur on all continents except Antarctica. The banded gecko (Coleonyx variegatus), the most widespread native North American species, grows to 15 cm (6 inches) and is pinkish to yellowish tan with darker bands and splotches. The tokay gecko (Gekko gecko), the largest species, attains a length of 25 to 35 cm (10 to 14 inches). It is gray with red and whitish spots and bands. The tokay gecko, native to Southeast Asia, is frequently sold in pet shops.