Just think of them as audio recordings, just like one would record on an old cassette player, but stored on the iPod. The advantage is podcasts offer the ability to have your iPod automatically download the latest show. Plug the iPod in to the computer and it syncs up with iTunes to download any new podcasts for any shows to which you subscribe.
OK, thanks, that's more concise than what I found on Wikipedia. Now, I was asking because while hunting for some legal MP3 in recent days I ran into offers of podcasts on various performers sites. But I was looking for MP3s of individual tunes, and it didn't seem to me that the podcasts were that, or that individual tunes could be extracted from them, so I passed...