Introduction

Usenet is one of the oldest computer network communications systems still in widespread use. It was established in 1980, following experiments from the previous year, over a decade before the World Wide Web was introduced and the general public got access to the Internet. It was originally conceived as a "poor man's ARPANET," employing UUCP to offer mail and file transfers, as well as announcements through the newly developed news software. This system, developed at University of North Carolina at Chapel Hill and Duke University, was called USENET to emphasize its creators' hope that the USENIX organization would take an active role in its operation .

The articles that users post to Usenet are organized into topical categories called newsgroups, which are themselves logically organized into hierarchies of subjects. For instance, sci.math and sci.physics are within the sci hierarchy, for science. When a user subscribes to a newsgroup, the news client software keeps track of which articles that user has read.

In most newsgroups, the majority of the articles are responses to some other article. The set of articles which can be traced to one single non-reply article is called a thread. Most modern newsreaders display the articles arranged into threads and subthreads, making it easy to follow a single discussion in a high-volume newsgroup.

When a user posts an article, it is initially only available on that user's news server. Each news server, however, talks to one or more other servers (its "newsfeeds") and exchanges articles with them. In this fashion, the article is copied from server to server and (if all goes well) eventually reaches every server in the network. The later peer-to-peer networks operate on a similar principle; but for Usenet it is normally the sender, rather than the receiver, who initiates transfers. Some have noted that this seems an inefficient protocol in the era of abundant high-speed network access. Usenet was designed for a time when networks were much slower, and not always available. Many sites on the original Usenet network would connect only once or twice a day to batch-transfer messages in and out.

Usenet has significant cultural importance in the networked world, having given rise to, or popularized, many widely recognized concepts and terms such as "FAQ" and "spam."

Today, almost all Usenet traffic is carried over the Internet. The current format and transmission of Usenet articles is very similar to that of Internet email messages. However, Usenet articles are posted for general consumption; any Usenet user has access to all newsgroups, unlike email, which requires a list of known recipients.

Today, Usenet has diminished in importance with respect to Internet forums, blogs and mailing lists. The difference, though, is that Usenet requires no personal registration with the group concerned, that information need not be stored on a remote server, that archives are always available, and that reading the messages requires not a mail or web client, but a news client (included in many modern e-mail clients).