A podcast is a type of digital media consisting of an episodic series of audio radio, video, PDF, or ePub files subscribed to and downloaded through web syndication or streamed online to a computer or mobile device. The word is a neologism derived from "broadcast" and "pod" from the success of the iPod, as podcasts are often listened to on portable media players. In the context of Apple devices, the term "Podcasts" refers to the audio and video version of podcasts, whereas the textual version of podcasts are classified under the app known as Newsstand.
A list of all the audio or video files currently associated with a given series is maintained centrally on the distributor's server as a web feed, and the listener or viewer employs special client application software, known as a podcatcher, that can access this web feed, check it for updates, and download any new files in the series. This process can be automated so that new files are downloaded automatically. Files are stored locally on the user's computer or other device ready for offline use, giving simple and convenient access to episodic content. In this way it is contrasted to webcasting (Internet streaming).
As discussed by Richard Berry, podcasting is both a converged medium bringing together audio, the web and portable media player, and a disruptive technology that has caused some in the radio business to reconsider some established practices and preconceptions about audiences, consumption, production and distribution. This idea of disruptiveness is largely because no one person owns the technology; it is free to listen and create content, which departs from the traditional model of 'gate-kept' media and production tools. It is very much a horizontal media form: producers are consumers and consumers become producers and engage in conversations with each other.