A Podcast is a digital medium that consists of an episodic series of audio or digital radio, subscribed to and downloaded through web syndication or streamed online to a computer or mobile device. The word is a neologism and portmanteau derived from "broadcast" and "pod" from the success of the iPod, as audio podcasts are often listened to on portable media players.
The Merriam Webster Tenth International Collegiate defines "Podcast" as: a program (as of music or talk) made available in digital format for automatic download over the Internet.
A list of all the audio or video files 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, which may seem to the user as if the content is being broadcast or "pushed" to them. Files are stored locally on the user's computer or other device ready for offline use. Podcasting contrasts with webcasting (Internet streaming), which generally isn't designed for offline listening to user-selected content.
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 of the 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.