Usenet is a world-wide distributed discussion system. It consists of a set of newsgroups with names that are classified hierarchically by subject.

Articles or messages are posted to these newsgroups by people on computers with the appropriate software -- these articles are then broadcast to other interconnected computer systems via a wide variety of networks. The articles generally expires in a few days, but now there are a number of usenet archives that keep the messages for posterity.

Some newsgroups are moderated; in these newsgroups, the articles are first sent to a moderator for approval before appearing in the newsgroup.

Usenet is available on a wide variety of computer systems and networks, but the bulk of modern Usenet traffic is transported over either the Internet or UUCP.