Newsgroups are typically found on USENET, a network of discussion groups where millions of users read postings, or articles, using software called a newsreader. Users can then make comments and ask questions in response to the postings. Thousands of newsgroups exist, covering a wide range of topics. Newsgroups typically fall into a few basic categories. There are newsgroups that have to be pre-approved and cover a specific topic, and there are alternative newsgroups that can be created by anyone and cover any topic of their choosing. Newsgroups are also categorized as either moderated—posts have to be approved—or unmoderated.

Newsgroup names are made up of parts, separated by dots, that indicate the topics covered in the newsgroup. The parts of the name go from least specific to most specific. For example, the group name comp.sys.apple2 discusses computers (a general topic), systems (a computer topic), and Apple II (a specific computer system). Some common group subjects are comp (computers), rec (recreation), and sci (science). Other newsgroups follow a similar order, including alternative groups, which start with alt.

Blogs (blog) and message boards have taken the place of many newsgroups, although newsgroups remain popular. In 2001 Google Inc., the American search engine company, acquired the archive of USENET postings, which go back to 1981. In addition to providing 20 years worth of USENET archives, the company introduced Google Groups to bring newsgroups to a new audience.