Rockford: What’s a podcast?
Nichole: Whatever you want it to be.
Rockford: What?
N: You can record something — like a radio show — and put it on the Internet.
R: So it’s an mp3.
N: Sort of, but it’s different. It’s like ham radio for the Internet.
R: You don’t know what a podcast is.
N: Do too.
(R gets a taste of N‘s wolverine ninja skills.)

According to Wikipedia:

Podcasting is a term used to describe a collection of technologies for automatically distributing audio programs over the Internet using a publisher/subscriber model. It differs from earlier online delivery of audio or video because it automatically transfers the digital media files to the user's computer for later use. Podcasting enables independent producers to create self-published, syndicated "shows," and gives broadcast radio or television programs a new distribution method.