Compared to television, an RSS feed can loosely be described as your TV program listing.
From the BBC website :
"RSS allows you to see when sites from all over the internet have added new content. You can get the latest headlines and articles (or even audio files, photographs or video) in one place, as soon as they are published, without having to remember to visit each site every day. It takes the hassle out of staying up-to-date, by showing you the very latest information that you are interested in."
With that in mind, every podcast uses an RSS feed that you can subscribe to using a "podcatcher" software such as iTunes and this podcatcher software will automatically download the podcast to your computer and your mp3 player.