BBS

BBS refers to Bulletin Board Systems, which were the equivalent of forums in the pre-web age.

Typically a user would dial-in to a BBS (ring a number via their modem) and be able to view and reply to posts made by others who had dialed in. Modern BBS' use the telnet protocol to connect users. They are famous in the Cyberpunk community, though lost their mainstream use in the early 2000's. BBS' weree famous for housing some of the world's greatest people, such as Richard Stallman, Dennis Richie, and many others. A large number of internet groups started on BBS, such as The Cult of the Dead Cow, The Church of the Subgenius, and etc.

8chan has an unofficial BBS shared with Lainchan and Endchan, available at https://slashtech.ch, running the Mystic BBS software on a NetBSD system.

BBS: The Documentary will give you a good perspective.