"Podcasting" is making audio files (most commonly in MP3 format) available online in a way that allows software to automatically download the files for listening at the user's convenience.

   The word "podcasting" is a portmanteau of the words iPod and broadcasting. A podcast is like an audio magazine subscription: a subscriber receives regular audio programs delivered via the internet, and they can listen to them at their leisure.

   Podcasts differ from traditional internet audio in two important ways. In the past, listeners have had to either tune in to web radio on a schedule, or they have had to search for and download individual files from webpages. Podcasts are much easier to get. They can be listened to at any time because a copy is on the listener's computer or portable music player (hence the "pod" in "podcasting"), and they are automatically delivered to subscribers, so no active downloading is required.

   Podcasting is functionally similar to the use of timeshift-capable digital video recorders (DVRs), such as TiVo, which let users record and store television programs for later viewing.

   Podcasting was developed in part thanks to former MTV VJ, Adam Curry's original iPodder script and the success it fostered since August, 2004.

   Podcasting was first used to directly describe the "automatic download and synchronization" idea developed by Adam Curry by Dannie J. Gregoire on September 15, 2004. Gregoire had registered the domain names associated with podcasting, podcasting.net. That usage was discovered and reported on by Dave Slusher of the Evil Genius Chronicles and Adam Curry.

   Adding to a number of ad-hoc, proto-podcasting techniques for automatically downloading audio files, podcasting proper became popular through association with blogs (in particular MP3 blogs), the XML-based file format called RSS (Really Simple Syndication), and the polling applications called feed readers or news readers that poll and download RSS files.

   Blogs, often being self-published websites, provided a convenient means for individuals to self-publish audio files online. RSS already gave websites and blogs a means to summarize or list new content added to the site. Individuals already used RSS to poll websites for new content. Thus, the addition of audio file listings to RSS, and the addition of audio file downloading to RSS feed readers built upon the feed reader's existing methods for polling and downloading files, and upon the existing "reader driven" interaction with content publishers.