What are Podcasts?
Podcasts are:Once subscribed (= the RSS-Feed is added to a program, called a Podcatcher), the computer downloads new episodes automatically. They are then saved on the computer and can be copied to other movable devices. That also explains the name: Podcast = iPod + Broadcasting
For more info:
How to subscribe to a Podcast
Using iTunes to subscribe to any Podcast:- Find the RSS-Feed of the Podcast (=the address of the Podcast), you wish to subscribe. Usually by clicking on one of these symbols (colors might vary):

These symbols can be found either in the address bar or on the webpage itself. - After clicking on these symbols, copy the Podcast's address
(e.g. http://gritmatthias.com/podcast/?feed=podcast) that usually appears in the browser's address bar.
- In iTunes, go to the menu bar to Advanced and click on Subscribe to Podcast...

- Paste the RSS-Feed (e.g. http://gritmatthias.com/podcast/?feed=podcast) into the pop-up window.
To paste you can use the key shortcut: 'CTRL+V' (for Windows), or 'Apple' + 'V' (for Mac OS X).
- Click OK, and the newest Episode of the Podcasts will be automatically downloaded under the category "Podcasts" in iTunes.

Some Podcasts also enable the automatic download via iTunes, which openes the Podcast in the iTunes Store, usually indicated through this symbol:
For more info: