Wikipedia defines a podcast as "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.
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.
This was alot for me to process considering I have never had any knowledge of podcasts.
I started off searching for some good examples of podcasts, but some of what I found didn't seem to follow the definition above.
One of the first examples I found seemed like a great educational use of podcasts, but after further scrutiny, I have decided this seems to be just a video, not a podcast.