Look for the feed icon:

RSS stands for Really Simple Syndication, and is an XML-based file format meant to be read by software programs. RSS is one of many web feed formats. Web feeds are useful because they allow website readers to track updates using an aggregator, instead of visiting the website all the time.

 Learn more about RSS at Wikipedia

A podcast has an RSS feed with enclosures (pointers to audio or video files) so that you don't have to visit the podcaster's website to get new episodes - they are automatically downloaded for you! All you need to do is use a "podcatcher", a software application that will subscribe to the RSS feeds for you, and automatically download the media files.

 Learn more about Podcatchers at Wikipedia

We use RSS at Podcast Spot to make it easier for you to subscribe to the newest podcasters, episodes, categories, and tags.