GA = the Geographical Association : the subject association for geographers...
RSS = Really Simple Syndication (or other things, such as Rich Site Summary, or "I'm Ready for Some Stories"...)
Basically, if you sign up to the RSS feed from the main GA website, you will get a digest of any changes to the site sent direct to your RSS reader, which might be your Google homepage for example...
The new GA RSS feed address is: http://feeds.feedburner.com/org/kOoa
Below is an excellent COMMONCRAFT explanation of how the process works....
Please update your RSS address if you were already subscribed...