What RSS actually stands for is a bit of a debate, but what it does has a much clearer answer. RSS is a way to "feed" a certain program live updates from dozens, even hundreds or thousands or separate websites, and funnel them all into a single location for you to browse. Websites such as CNN, Wired, SciFi Wire, Universities and pretty much any site that publishes numerous updates has an RSS feed these days.
What happens is this: You download an RSS Reader (also called an Aggregator) and install it on your computer (FeedReader). Or, you sign up for a free service on the web (NewsGator, GoogleRSS, still in beta). Inside your particular program you then "subscribe" to certain "feeds" from other websites. For instance, to subscribe to PaintStik's RSS you would enter the URL http://www.PaintStik.com/rss.php for the feed. Add as many feeds as you want or from any website that offers them!
Once your feeds have been added to the program, the program takes care of the rest of the work for you. Periodically (how often depends on your program settings) the RSS Reader will automatically go out to all of your feeds and pull in any new items that have been posted there. The "headlines" and descriptions of those items are then displayed in your reader, along with a link to the website they came from in order to read the full story. Presto, instant news subscriptions to your favorite websites without having to bookmark and visit each one every day/hour/minute!
That's all there is to it! Now, if you already have an RSS reader, subscribe to PaintStik's feed with http://www.PaintStik.com/rss.php or by dragging this icon: to your reader.