RSS is a technology that allow Internet users to subscribe to websites that have provided RSS feeds, (content on your site that updates regularly.)
Since computer users are always looking for information, and website owners are always looking for content, this is another way to add exposure to your business.
A few resources....
http://www.rsspublisher.com/ (creating feeds)
http://blogspace.com/rss/readers (desktop readers)
http://www.geckotribe.com/rss/carp/manual/ (re-publish rss feeds on your website)
If you have a blog, rss features are usually built-in with the blog software.