What's a Podcast?
A podcast is a series of digital media files, usually digital, audio, or video, that is made available for download via web syndication. The syndication aspect of the delivery is what differentiates podcasts from other files that are accessed by simple download or by streaming: it means that special client software applications known as podcatchers (such as Apple Inc.'s iTunes or Nullsoft's Winamp) can automatically identify and retrieve new files when they are made available, by accessing a centrally-maintained web feed that lists all files associated with a particular podcast. The files thus automatically downloaded are then stored locally on the user's computer or other device, for offline use. (Wikipedia)