PodCasting

http://en.wikipedia.org/wiki/podcasting

Podcasting is a method of publishing audio broadcasts via the Internet, allowing users to subscribe to a feed of new files (usually MP3s). It became popular in late 2004, largely to automate downloading of audio onto portable players or personal computers. The word "podcasting" is a portmanteau that combines the words "broadcasting" and "iPod." The term can be misleading since neither podcasting nor listening to podcasts requires an iPod or any portable music player. For that reason, since September 2004 various writers have suggested reinterpreting the letters POD to create "backronyms" such as "Personal On-Demand."[1] However, the word is rarely presented as "PODcasting."
Podcasting is distinct from other types of online media delivery because of its subscription model, which uses the RSS 2.0 XML (or RDF XML) format to deliver an enclosed file. Podcasting enables independent producers to create self-published, syndicated "radio shows," and gives broadcast radio programs a new distribution method. Listeners may subscribe to feeds using "podcatching" software (a type of aggregator), which periodically checks for and downloads new content automatically. Some podcatching software is also able to synchronise (copy) podcasts to portable music players. Any digital audio player or computer with audio-playing software can play podcasts. The same technique can deliver video files, and by 2005 some aggregators could play video as well as audio.