The name Atom applies to a pair of related standards. The Atom Syndication Format is an XML language used for web feeds, while the Atom Publishing Protocol (APP is the acronym, but it is referred to as 'AtomPub' for short) is a simple HTTP-based protocol for creating and updating Web resources.

Web feeds allow software programs to check for updates published on a web site. To provide a web feed, a site owner may use specialized software (such as a content management system) that publishes a list (or "feed") of recent articles or content in a standardized, machine-readable format. The feed can then be downloaded by web sites that syndicate content from the feed, or by feed reader programs that allow Internet users to subscribe to feeds and view their content.

A feed contains entries, which may be headlines, full-text articles, excerpts, summaries, and/or links to content on a web site, along with various metadata.

The development of Atom was motivated by the existence of many incompatible versions of the RSS syndication format, all of which had shortcomings, and the poor interoperability of XML-RPC-based publishing protocols. The Atom syndication format was published as an IETF "proposed standard" in RFC 4287. The Atom Publishing Protocol is still in draft form.