Yes, podcasts are an audio form of RSS. Of course, most people aren't familiar with RSS either. I just did a study about RSS for work and learned about it that way.
Podcasts are audio that can be subscribed to and then are automatically sent to you on a regular basis. I subscribed to the Ebert & Roeper podcast on iTunes and every Monday when I get to work, I open iTunes and the newest week's show is automatically downloaded. I usually then listen to it at work, but it can also be transferred to an iPod or MP3 player. Podcasts usually aren't music because most podcasts are created by random people and can't get the rights, but a lot of underground music may be delivered this way. You tend to find a lot of podcasts about politics, sports, newest technology, and there are even a few weekly Harry Potter talk shows. As far as I know, all (or at least most) podcast subscriptions are free.