A discussion group on the Internet. Just as e-mail and the Web are two distinct services on the Internet, newsgroups are part of the "Usenet" (user network), which is another service, or facility, on the Internet. Although a newsgroup topic can be newsworthy, newsgroups have nothing to do with the daily news; thus, the term is somewhat misleading.

Newsgroups are organized into categories and subcategories, with the alt (alternative) category having the most diversity (see newsgroup categories). Preceding the Web by more than a decade, newsgroups started in the late 1970s as a message board for Unix and related technical issues. They continue to prosper alongside the Web, although the Web has its own discussion groups (see forum).

Newsgroups start by someone posting an initial query or comment. As others reply, the text forms a chain of related postings called a "message thread." Newsgroups are similar to blogs, but usually have more questions and answers, whereas the blog is often used for general commentary (see blog). Newsgroups are also a source for MP3 files and pictures (see newsgroup categories).

Newsreader software (an NNTP client) is used to "subscribe" to newsgroups and read and post messages. A newsreader, which may be a stand-alone application or part of an e-mail program or Web browser, offers many features such as searching for and automatically subscribing to newsgroups that match some criteria.

The Usenet Network
Some newsgroups are moderated; some are not. They originate from many sources and are hosted on many systems. With more than 100,000 newsgroups, an ISP may decide which newsgroups, if any, to offer customers and how long postings remain online. There are also dedicated Usenet providers that do not discriminate and store most newsgroups indefinitely. See NNTP, Deja.com, syndication format and newsgroup categories.