RSS is a family of web feed formats, specified in XML and used for Web syndication. RSS is used by (among other things) news Web sites, weblogs and podcasting. The abbreviation is variously used to refer to the following standards:

* Really Simple Syndication (RSS 2.0)
* Rich Site Summary (RSS 0.91, RSS 1.0)
* RDF Site Summary (RSS 0.9 and 1.0)

Web feeds provide web content or summaries of web content together with links to the full versions of the content, and other metadata. RSS, in particular, delivers this information as an XML file called an RSS feed, webfeed, RSS stream, or RSS channel. In addition to facilitating syndication, web feeds allow a website's frequent readers to track updates on the site using an aggregator.
Source: Wikipedia