Sorry, guess I assumed everyone knew about them. We all know what happens when you assume.
They are as Tarpley said. I am using them as a subscription. It works sort of like when you post to a thread and then you get alerts of new posts. I can insert the RSS Feed (which is usually coded in XML) into my homepage and instead of the default headlines from CNN or AP, I can get Fox News, Washington Times, WSJ etc.
There are RSS feeds for practically everything. News, Sports, Entertainment, Blogs, etc. You can insert them into your web page and basically build your own personalized online newspaper.