What is Usenet

1 About Usenet
1.1 What is Usenet?
Usenet is a distributed network which means that the submitted information
is always available via the fast internet connections from your local Usenet
Provider.
Usenet offers the ability to efficiently exchange information among all
other Usenet users around the globe.

Usenet, which is short for Unix User Network, is one of the oldest
communication networks, being developed in 1979 and was made available
before the internet and the World Wide Web were invented. Usenet isn't
governed by any authority and can be characterized by the absence of a
central server or administrator.
Usenet servers distribute all the information they receive among other
Usenet servers around the world, enabling all Usenet users to have access to
all information available on the global Usenet.

Usenet was designed to be able to discuss scientific insights and ideas
among universities and scientific institutions around the world on a broad
scope. Therefor Usenet was designed to distribute only text messages. In
1990 a method was introduced to be able to decode files (like documents or
images) to text, so they could be distributed on the global Usenet.

Every post submitted to Usenet has to be stored by all Usenet servers. This
results in a continuous flow of new Usenet articles.
As the Usenet servers storage capacity isn't unlimited, older articles have
to be removed in order to make room for newer articles.
The period of time that articles are available is called retention.
As different Usenet providers have different storage capacities, the
retention differs per Usenet provider.
The retention of Usenet services offered by Internet providers (ISPs) is
significant lower (on average 10-20 days) then the retention offered by
professional Usenet providers (hundreds of days).

Being one of the oldest networks, Usenet has survived many new innovations.
At present, Usenet's popularity is still growing, while more and more people
discover the advantages of using Usenet. As more people are becoming active
on Usenet, more information is offered to the global Usenet. The daily
newsfeed (which is the amount of data offered to Usenet on a daily basis) is
now well beyond 5 terabyte on average (winter 09/10).

Usenet is known by many names. Synonyms for Usenet are Newsgroups, News or
Newsserver.

http://www.news-service.com/faq.html#faq1.1