podcasting is creating an audio file (traditionally in MP3 format, though other formats can be used as well) and making it available online for other people to listen to. If that were all there was to it, you would probably say “So what? That capability has been around for years!” and you would be correct. What’s different now is that there are simple ways to subscribe to specific shows and have the audio files automatically downloaded to your computer and placed into your MP3 software - likely iTunes on the Mac - and, thus, if you wish onto your MP3 player - probably an iPod - without any effort. Simplifying and automating that task has made all the difference.

Right off the bat, I want to clear up one common misconception about podcasting: it has essentially nothing to do with the iPod, and you do not need an iPod to listen to podcasts. If another MP3 player was the cool toy everyone had to have, podcasting would have been given a different name.

From TidBITS.