RSS stands for Really Simple Syndication. It is a way of getting website updates automatically. In order to use RSS, you will need a feed reader. Your browser may have a feed reader built-in. For more information about RSS and feed readers see wikipedia’s entry for RSS and the entry for feed readers (here called aggregators).
When you follow a link for a feed, what you see will be an unformatted page of text and pictures. You’ll want to plug the url for the feed that you want to follow into your feed reader. Orion offers RSS 2.0 feeds and Atom feeds. Check your feed reader for which you want to use; for many it won’t matter which you choose.
If your browser shows a feed symbol in the address bar, you can subscribe to feeds by clicking on it: