Its a way of knowing whats new on a particular site - without actually going on the site. For example, I use Firefox and have it set up for this site - so when a new post comes in - Firefox tells me. I can read a certain amout or click the link to take me to the message.
ANother way to get it is to download the FHUK Toolbar - it has the RSS links already linked in ready for you.
Heres some links about RSS:
What is RSS?
As defined by Wikipedia, RSS (acronymic for Really Simple Syndication) is "a group of XML based web-content distribution and republication (Web syndication) formats primarily used by news sites and weblogs (blogs)." Essentially, an RSS feed is a hosted XML file from which your RSS newsreader pulls headlines, URLs, and other content as it is updated.
Need RSS software?
To get started, you'll need to download and install a free RSS newsreader client. Many are available (some as browser extensions); see Google's list here. Point your software to RSS feeds of interest, and you're done!