From Rss @ Wikipedia: "RSS is a family of Web feed formats used to publish frequently updated content such as blog entries, news headlines, and podcasts.[2] An RSS document (which is called a "feed" or "web feed" [3] or "channel") contains either a summary of content from an associated web site or the full text. RSS makes it possible for people to keep up with web sites in an automated manner that can be piped into special programs or filtered displays."
simple words. people can read half/full content of the rss feed subscribed site on their pc without visiting the site.