A podcast is a digital media file, or a series of such files, that is distributed over the Internet using syndication feeds for playback on portable media players and personal computers. A podcast is a specific type of webcast which, like 'radio', can mean either the content itself or the method by which it is syndicated; the latter is also termed podcasting. The host or author of a podcast is often called a podcaster. The term "podcast" is a portmanteau of the name of Apple's portable music player, the iPod, and broadcast[1]; a "pod" refers to the iPod, and "cast" to the idea of broadcasting.

In other words, a podcast is a collection of files (usually audio but may include video) residing at a unique web feed address. People can "subscribe" to this feed by submitting the feed address to an aggregator (like iTunes - software that runs on the consumer's computer). When new "episodes" become available in the podcast they will be automatically downloaded to that user's computer. Unlike radio or streaming content on the web, podcasts are not real-time. The material is pre-recorded and users can check out the material at their leisure, offline.

Though podcasters' web sites may also offer direct download or streaming of their content, a podcast is distinguished from other digital media formats by its ability to be syndicated, subscribed to, and downloaded automatically, using an aggregator or feed reader capable of reading feed formats such as RSS or Atom.

Certain podcasts, can even be live and interactive. Dozens of podcast enthusiasts can be on at once, with the "host" being able to control their audience in the same way a radio host can.

Open culture posted a nice Podcast Primer, but more geared towards how to subscribe and listen to podcasts.

What Is Podcasting by Phillip Torrone

Make Your Own Podcast

Setup

Podcast Production Step-by-Step

Podcasting for Learning by Aixa Almonte, Podcast Producer and Kathleen Gilroy CEO, The Otter Group [PDF]. Context, tips, tools and more.

Top Business Schools Open Podcasts

1. Knowledge@Wharton from Wharton at The University of Pennsylvania (iTunes - Feed - Web Site)
2. HBR IdeaCast (iTunes Feed) from Harvard Business School
3. Duke’s Fuqua School of Business (iTunes - Web Site)
4. The University of Chicago Graduate School of Business (iTunes Feed Web Site)
5. Stanford’s “Entrepreneurial Thought Leaders,” [I blogged about it few months back]

Here goes the complete list at Open Culture for university podcast collection

Vodcast or Vidcast

Video podcast (sometimes shortened to vidcast or vodcast) is a term used for the online delivery of video on demand video clip content via Atom or RSS enclosures. The term is an evolution specialized for video, coming from the generally audio-based podcast and referring to the distribution of video where the RSS feed is used as a non-linear TV channel to which consumers can subscribe using a PC, TV, set-top box, media center or mobile multimedia device.

Slidecast