What Happens with a Podcast
Here's a spoiler alert, in case you haven't figured it out yet: The basic purpose of the Internet is to provide hundreds of thousands of jerks, dweeks, geeks, freaks, flakes, egotists, ignoramuses, nutjobs, loners, twits, arrogant pinheads, and delusional Travis Bickle aficionados a way to share their unique articulations of individual insanity with a potential audience of millions of total strangers.
Podcasting was invented when members of the above groups realized that the human population could insulate themselves from these messages by simply sealing themselves inside a metal automobile or any place where Wi-Fi signals can't penetrate or where Internet users can't read text.
Still, as podcasting became part of mainstream communication, the level of content available via podcast was raised. Now, the same shows you tune in to all the time on public radio, local stations, and national TV networks can arrive on your desktop (and thence your iPhone or iPod Touch) at regular intervals at no charge.
I should warn you that the folks who podcast from major networks and the like are (generally speaking) no less stable or egotistical than the Internet freelancers. But at least you know they're probably making a comfortable living. A full belly tends to stifle baser urges to inflict stress and mayhem upon society.