WHAT IS PODCASTING?

Podcasting is quickly becoming a buzz word among the techie crowd. So what is podcasting, anyway? Podcasting is online audio content that is delivered via an RSS feed. Many people liken podcasting to radio on demand. However, in reality, podcasting gives far more options in terms of content and programming than radio does. In addition, with Podcasting, listeners can determine the time and the place, meaning they decide what programming they want to receive and when they want to listen to it.

Listeners can retain audio archives to listen to at their leisure. While blogs have turned many bloggers into journalists, podcasting has the potential to turn podcasters into radio personalities.

Podcasting is the syndication of audio files using RSS. Podcasting works the same as a standard RSS feed reader or news aggregator, the only difference is that the feed you subscribe to contains an audio file in it. Instead of reading content in your RSS feed reader or aggregator, you can listen to the contents of your feed using a reader or aggregator that supports podcasting, or you can listen to them on an iPod or similar device. While podcasting was named for the iPod, you do not have to have an iPod to listen to a podcast. Podcasts can be displayed on websites with clickable links to audio files and many of the standard RSS readers.

The audio file that makes the feed a podcast rather than a standard RSS feed is contained in the 'enclosure' tag. The easiest way to think of this is as an e-mail attachment.
(From What is Podcasting?)