Usenet is the set of machines that exchange articles tagged with one or more universally-recognized labels, called newsgroups (or "groups" for short). (Note that the term newsgroup is correct, while area, base, board, bboard, conference, round table, SIG, etc. are incorrect. If you want to be understood, be accurate.)
The Diversity of Usenet If the above definition of Usenet sounds vague, that's because it is. It is almost impossible to generalize over all Usenet sites in any non-trivial way. Usenet encompasses government agencies, large universities, high schools, businesses of all sizes, home computers of all descriptions, etc. Every administrator controls his own site. No one has any real control over any site but his own. The administrator gets his power from the owner of the system he administers. As long as the owner is happy with the job the administrator is doing, he can do whatever he pleases, up to and including cutting off Usenet entirely.