Usenet is an online, distributed, threaded discussion system on the Internet established in 1980.
Usenet is split up into a number of hierarchies. The "Big 8" consist of:
In addition, there are a number of other hierarchies. The biggest of these is the alt hierarchy. The Big 8 hierarchies are managed by the Big 8 Management Board, while the alt hierarchy has no such governing body - although it does have a rough consensus-driven approach for newsgroup creation. A number of country-specific hierarchies exist - japan.*, uk.*, ne.* etc. Many ISPs and companies have their own newsgroups - Microsoft.*, for instance - although these are often not distributed to the wider Usenet.
Usenet, as one of the first and longest-running discussion forums, has created a distinct culture and community around it. Trolling and flaming - often under the cloak of (pseudo-)anonymity, while widely considered to be negative behaviours, have become an art form for many (the parellels exist with smack talk or trash talk). The topics which set off flame wars are often niche technical topics of interest - "religious wars" between proponents of different operating systems, text editors or programming languages.
The infusion of newbies on to the network every September eventually culminated in the "September that never ended" when, in 1993, AOL allowed their users to access Usenet.
Many ISPs are no longer providing Usenet access on their local servers - due to the ever-increasing popularity of the Web and other services on the network, and because many users of Usenet only use it to get binaries - which can be very large and also have legal issues (many binaries infringe on copyright law, others break laws against child pornography or other illicit material). Usenet is slowly becoming a niche service, with many users needing to get access through premium-rate Usenet providers (for binaries) or third-party servers (for text).