The Jargon File (version 4.4.7, 29 Dec 2003):
The Free On-line Dictionary of Computing (30 December 2018):
(Plural "fora" or "forums") Any discussion group
accessible through a dial-in BBS (e.g. GEnie, CI$), a
mailing list, or a Usenet newsgroup (see network,
the). A forum functions much like a bulletin board; users
submit postings for all to read and discussion ensues.
Contrast real-time chat or point-to-point personal e-mail.