A podcast is an audio broadcast on the Internet. The reason it's called a podcast is because people can download the audio file to listen on their iPods. However, you don't need an iPod to listen to a podcast. You can use a computer or any portable musci player as long as it is able to play digital audio files like mp3s. If you can play music on your computer, your computer can play a podcast.
One advantage that podcasts have over regular audio files is the ability to subscribe to a podcast rather than find them on the Internet and download them. Every time there is a new podcast, the player can automatically download the file to listen to later.
