Warhammer 40k - Lexicanum:Atom
Atom (or Atom Syndication Format for long) is an XML language used for web feeds.
Purpose
The Lexicanum Atom web feed allows software programs to check for updates published on the Lexicanum. It can be downloaded by programs that use it, like websites that syndicate content from the feed, or by feed reader programs that allow internet users to subscribe to feeds and view their content. The blogging community uses web feeds to share recent entries' headlines, full text, and even attached multimedia files.
A feed reader or "aggregator" program can be used to check feeds and to display new articles. Client-side readers may also be designed as standalone programs or as extensions to existing programs like web browsers. Web-based feed readers and news aggregators require no software installation and make the user's "feeds" available on any computer with web access.
Further reading
To learn more about Atom go here.