A newsgroup is a repository within the Usenet system for messages posted from many users at different locations. The term is somewhat confusing, because it is usually a discussion group. Newsgroups are technically distinct, but functionally similar to discussion forums on the World Wide Web.
Newsgroups are arranged into usenet hierarchies, theoretically making it simpler to find related groups. The term Top-level usenet hierarchy refers to a usenet hierarchy defined by the prefix prior to the first dot. So for instance newsgroup rec.arts.sf.starwars.games would be in the rec.* usenet hierarchy. There are eight major hierarchies of newsgroups, known as the "Big 8":
- comp.* - Discussion of computer-related topics
- news.* - Discussion of Usenet itself
- sci.* - Discussion of scientific subjects
- humanities.* - Discussion of the humanities (e.g. literature, philosophy)
- rec.* - Discussion of recreational activities (e.g. games and hobbies)
- soc.* - Socialising and discussion of social issues.
- talk.* - Discussion of contentious issues such as religion and politics.
- misc.* - Miscellaneous discussion - anything which doesn't fit in the other hierarchies.
The alt.* hierarchy has discussion of all kinds of topics, and many hierarchies for discussion specific to a particular geographical area or in a language other than English.
Before a new Big 8 newsgroup can be created, it must be discussed in the newsgroup news.groups, and it must be voted on - anyone is allowed to vote. The vote will only pass if at least two-thirds of all votes cast are in favour and there are 100 more votes in favour than against. Creating a new group in the alt.* hierarchy is not subject to such strict rules, but it should be discussed in alt.config first.
Typically, a newsgroup is focused on a particular topic such as 'shellfish'. 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 tend to come in two types, binary and text, there is no technical difference between the two, but the differentiation means that users and server who only have limited facilities can avoid downloading large binaries.
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.
There are currently well over 100,000 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 several thousand) messages a day.
A website called Deja News began archiving Usenet and also provided a searchable web interface to it in the 1990s. Google bought the archive off them and also made efforts to buy other Usenet archives to attempt to create a complete archive of Usenet newsgroups and postings from its early beginnings. Google also has a web search interface to the archive and also allows newsgroup posting.
See also: List of newsgroups