The Usenet is a loose term for the many thousands of newsgroups which
are propagated around the world using a set of protocols that allows
many different pieces of software to work together.  With so many
different newsgroups, each newsgroup usually has a specific topic
which it is intended for.  Often, the newsgroup name hints at what
that topic is; in other cases, the newsgroup's charter, if it has one,
can help clarify the purpose of the newsgroup.

It has always been a problem on the Usenet that people will sometimes
post their articles to inappropriate newsgroups, although certainly
with the vast increase of the number of people who have access to the
Usenet (through the explosion in the Internet, the accessibility of
Usenet from major on-line service providers like Compuserve, AOL, and
Prodigy, etc.) this problem has gotten worse.

In some cases, the people who post in inappropriate newsgroups are
making an honest mistake --- perhaps they honestly didn't understand
what the newsgroup's topic was, or perhaps their software got confused
or confused them.  In other cases, people deliberately post into
inappropriate newsgroups, not caring that they are contributing noise
and therefore making the newsgroup a less useful place for those who
subscribed to discuss the intended topic.  (People who post
advertisements, chain letters, or ideological rantings often fall into
this latter category.)

If you see an inappropriate posting in a Usenet newsgroup (and in
particular, this one), please restrain yourself from following up with
a posting complaining that such postings are inappropriate.  Consider
that if a mere 1% of the readers of this newsgroup were to do so, each
inappropriate posting would be followed by hundreds of complaint
postings, each of which would also be off-topic.  Instead, consider
sending email to the person who posted inappropriately and ask that
they refrain from posting in newsgroups where their postings are not
on-topic, and to consider cancelling their postings.  (Sometimes
people don't know how to cancel their postings; if they don't know,
they should ask their local site's system administrators for help.)

If the off-topic nature of the posting is particularly aggregious or
repeated, you may wish to consider also complaining to their local
site's system administrators directly.  If their email address is
"someuser@some-address.com", for example, likely addresses you may
wish to consider complaining to are (listed in order of preference)
usenet@some-address.com, postmaster@some-address.com, and
root@some-address.com.  Some sites' administrators are very good about
leaning on their users to follow the accepted conventions of posting
only in appropriate newsgroups; other sites are not so neighborly.

[Source: Ping Huang <pshuang@mit.edu>.]