Really Simple Syndication (RSS) is an XML based format used for content distribution and syndication.
Subscribing to RSS Feeds allows you to receive custom, up-to-date information from your favorite online content sources without having to regularly check the site for updates.
How do I use RSS?
Most browsers have an orange RSS button. Just click on that to add the feed to your browser live links.
You can also add feeds to customized home pages such as iGoogle and Microsoft Live by copying the feed url and pasting it into the correct "add to this page" area of that site.
More information about RSS is available at Wikipedia.