Usenet is a network message sharing system that exchanges messages in a
standard format.  Messages are arranged into topical categories called
newsgroups.  Newsgroups can be thought of as analogous to the channels
in broadcast television.  The messages contain plain text information
(which may include encoded binary information) and a series of headers
that define who the message came from, when the message was posted,
where it was posted, where it has passed, and other administrative
information.

Usenet/Netnews is a dual entity.  On one level is it merely the messages
being passed from machine to machine using known protocols. On another
level is it the people (the readers and posters of the messages) who
interact with the computers.  Care should be taken to not get too
confused when people talk about "Usenet is...." because of this duality.
Usenet should not be mistaken for any underlying transport mechanisms that
provide other services in addition to the transfer of the messages.
That is, Usenet is not UUCP, Usenet is not a particular network or set
of networks (e.g. the Internet).

One should also be careful to not confuse Usenet with any particular
group of users.  That is, Usenet is *not* an american network, Usenet is
not a network of computer scientists, and Usenet is not a network of
system administrators.  It is a complete cross-section of all the sorts
of folks who use computers either for work or play.  English *is* the
common language of Usenet, but there is no guarantee that the users
*know* english particularly well. :-)

By one popular definition, Usenet is the newsgroups in the major
categories of comp, misc, news, rec, sci, soc, and talk.  There are a
number of other major "hierarchies" which may be worldwide (alt, bionet,
vmsnet),  regional (usa, can, triangle), or even organizational
(duke, ut, sun).  These message hierarchies use the NetNews protocols,
and are colloquially called "Usenet", but purists can (and do) argue for
days about the distinctions.  I tend to use the term "NetNews" to refer
to the whole suite of programs and all the newsgroups in conglomeration.

There is not enough room here to fully discuss the ins and outs of
NetNews.  There are several NetNews groups that are dedicated to
discussion of NetNews itself.  (news.* and alt.culture.usenet are
examples, the `*' refers to any newsgroup that begins its name with a
string of "news.")

There are additional regular FAQ (frequently asked questions) postings
in the newsgroup "news.announce.newusers" and the newsgroup "news.answers"
that provide much more information about this topic.