Podcasting isn’t just putting an audio file on a website…
To start podcasting you create an audio file and make it available via the Web … but that’s not yet the whole of podcasting (it’s just an audio file on the Web).
As a colleague explained to me yesterday, an important element of podcasting is the subscription element. Users “subscribe” to the podcast and a “podcatcher” program downloads the cast automatically when there is new content. So you don’t just go to a page to click on a new cats. A podcast can still be a one-off. It’s similar to an RSS feed. And the podcast feed (techie = enclosure in an XML file) can include not just audio but video, images, documents… of course those wouldn’t be playable on your MP3 player so you’d need something a bit more
Podcasts can be labelled with tags and keywords so that they can be found by search engines. They can be made available from your server via various download sites, the most obvious being Apple iTunes. So this is what makes it a podcast rather than just another audio file to download.
Here’s a lucid description by David Czepanski (Apple warning!):