RSS (Rich Site Summary) is a format for delivering regularly changing web content. Many news-related sites, blogs and other online publishers syndicate their content as an RSS Feed to whoever wants it.
RSS solves a problem for people who regularly use the web. It lets you easily stay informed by retrieving the latest content from the sites you're interested in. You save time by not needing to visit each site individually and ensure your privacy, by not needing to join each site's email newsletter. The number of sites offering RSS feeds is growing rapidly.
A variety of RSS readers are available for different platforms. Some popular readers include Amphetadesk (Windows, Linux, Mac), FeedReader (Windows), and NewsGator (Windows; integrates with Outlook).
There are also a number of web-based feed readers available. My Yahoo, Bloglines, and Google Reader are popular web-based feed readers.
Once you have your feed reader, it's a matter of finding sites that syndicate content and adding their RSS feed to the list of feeds your reader checks. Many sites display a small icon with the acronyms RSS, XML, or RDF to let you know a feed is available.