RSS stands for "Really Simple Syndication", and is a data format designed to be readable by a variety of pieces of software. For humans it's particularly useful when used with "reader", or "aggregator" software. This software helps you know when there are new items published from our web site.
For more information about RSS and readers, take a look at these links from Wikipedia.
Any time you see this icon: you can click on it to get whatever RSS feed is available. Look for it on web sites, in Internet Explorer 7, and Firefox.
A podcast is simply an RSS feed with an mp3 audio file attached to each item in the feed. You may subscribe to the podcast with a standard RSS reader, or if you happen to have a portable audio device you can set it up to download each piece of audio automatically.