Podcasts can be thought of as shows, either video or radio shows. They cover certain topics you may be interested in. For me, I subscribe to a variety of Web Design and Technology related podcasts.
There are thousands to choose from, using websites such as poodle.fm and the Yahoo Podcast directory will help you discover new podcasts. Apple's iTunes program also has a large variety of different podcast shows, you can learn more information about this on this page by Apple.
Below is a list of the podcasts I subscribe to: