A podcast is a series of digital media files, usually either 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 ways of accessing files, such as simple download or 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 in a series when they are made available, by accessing a centrally-maintained web feed that lists all files currently associated with that particular podcast. The files thus automatically downloaded are then stored locally on the user's computer or other device, for offline use.

Like the term broadcast, podcast can refer either to the content itself or to the method by which the content is syndicated; the latter is also called podcasting. A podcaster is the person who creates the content.

The term is a portmanteau of the words "iPod" and "broadcast",[1] the Apple iPod being the brand of portable media player for which early podcasting scripts were developed (see history of podcasting), allowing podcasts to be automatically transferred from a personal computer to a mobile device after they are downloaded.[2] Despite the source of the name, it has never been necessary to use an iPod, or any other form of portable media player, to use podcasts; the content can be accessed using any computer capable of playing media files.[3] As more mobile devices other than iPods became able to synchronize with podcast feeds, a backronym developed where podcast stood for "Personal On Demand broadCAST."