The term podcast is a combination of the words iPod (as the Apple iPod was the first portable media player for which these type of files were developed) and the word broadcast. Podcasts are audio or video files which can be downloaded for later listening/viewing. For example, a professor can record a class session, create a podcast of the recording, and allow their students to download and listen to it as a review.
Podcasts also often work in conjunction with Really Simple Syndication (RSS) allowing listeners to subscribe to the feed thus allowing new podcasts to be automatically accessed as they become available. This can be done either through a RSS enabled web browser/email client, a stand-alone RSS reader, or an RSS enabled media application, such as iTunes.
Once the files are downloaded to the local machine they can then be synced to your portable media player or listened to through iTunes or other audio/video players.Podcasts can be as simple as an .mp3 audio file, an enhanced AAC .m4a file, which allows for embedding hyperlinks and still images, or video files of the following formats - .mov, .mp4, and .m4v. You can even podcast .pdf files. (Some formats and types will not work on portable media players, but all will work from within iTunes.)
For further information or to request an account, please contact mike@uri.edu, or visit the URI Podcasting site listed below.
Links:
Apple's "Making a Podcast" tutorials.
Wikipedia's definition of Podcast.