A newsgroup is a repository usually within the Usenet system, for messages posted from many users in different locations. The term may be confusing to some, because it is usually a discussion group. Newsgroups are technically distinct from, but functionally similar to, discussion forums on the World Wide Web. Newsreader software is used to read newsgroups.

Types of newsgroups

Typically, a newsgroup is focused on a particular topic . Some newsgroups allow the posting of messages on a wide variety of themes, regarding anything a member chooses to discuss as on-topic, while others keep more strictly to their particular subject, frowning on off-topic postings. The news admin (the administrator of a news server) decides how long articles are kept before being expired (deleted from the server). Usually they will be kept for one or two weeks, but some admins keep articles in local or technical newsgroups around longer than articles in other newsgroups.

Newsgroups generally come in either of two types, binary or text. There is no technical difference between the two, but the naming differentiation allows users and servers with limited facilities the ability to minimize network bandwidth usage. Generally, Usenet conventions and rules are enacted with the primary intention of minimizing the overall amount of network traffic and resource usage.

Newsgroups are much like the public message boards on old bulletin board systems. For those readers not familiar with this concept, envision an electronic version of the corkboard in the entrance of your local grocery store.

Newsgroups frequently become cliquish and are subject to sporadic flame wars and trolling, but they can also be a valuable source of information, support and friendship, bringing people who are interested in specific subjects together from around the world.

Back when the early community was the pioneering computer society, the common habit seen with many articles was a notice at the end disclosed if the author was free of, or had a conflict of interest, or had any financial motive, or axe to grind, in posting about any product or issue. This is seen much less now, and the reader must read skeptically, just like in society, besides all the privacy or phishing issues.

There are currently well over 100,000 Usenet newsgroups, but only 20,000 or so of those are active. Newsgroups vary in popularity, with some newsgroups only getting a few posts a month while others get several hundred (and in a few cases a couple of thousand) messages a day.

Weblogs have replaced some of the uses of newsgroups (especially because, for a while, they were less prone to spamming).

A website called Deja News has begun archiving Usenet in the 1990s. DejaNews also provided a searchable web interface. Google bought the archive from them and made efforts to buy other Usenet archives to attempt to create a complete archive of Usenet newsgroups and postings from its early beginnings. Like DejaNews, Google has a web search interface to the archive, but Google also allows newsgroup posting.