The New York Times writes in the aftermath of Apple’s entry into the business:
“Podcast” is an ill-chosen portmanteau that manages to be a double misnomer. A podcast does not originate from an iPod. And it is not a broadcast sent out at a particular time for all who happen to receive it.
It is nothing other than an audio or video file that can be created by anyone – add a microphone to your computer, and you’re well on your way. The file begins its public life when you place it on a Web site, available for anyone to download to a computer and, from there, to transfer to a portable player, which may or may not be an iPod. It’s encoded in such a way that the receiving computer can pick it up in successive installments automatically, whenever they are posted to the Web site. Subscribing is the term used for the automatic downloads, and it’s apt.
The delivery mechanism for a podcast subscription is rather slick. There’s no need to go to the trouble of browsing the Web site again for fresh material: the new stuff moves without so much as a beep from the original server to your computer. Then it moves automatically to your attached portable player, keeping the content perpetually refreshed. Welcome to the post-Web era.