A podcast is a program made available in digital format for download over the Internet. For example, an episodic series of digital audio files that a user can download to a personal device to listen to at a time of their choosing. Podcasts are primarily an audio medium, with some programs offering a supplemental video component. Streaming applications and podcasting services provide a convenient and integrated way to manage a personal consumption queue across many podcast sources and playback devices. There are also podcast search engines, which help users find and share podcast episodes. A podcast series usually features one or more recurring hosts engaged in a discussion about a particular topic or current event. Discussion and content within a podcast can range from carefully scripted to completely improvised. Podcasts combine elaborate and artistic sound production with thematic concerns ranging from scientific research to slice-of-life journalism. Many podcast series provide an associated website with links and show notes, guest biographies, transcripts, additional resources, commentary, and occasionally a community forum dedicated to discussing the show's content. The cost to the consumer is low, with many podcasts free to download. Some podcasts are underwritten by corporations or sponsored, with the inclusion of commercial advertisements. In other cases, a podcast could be a business venture supported by some combination of a paid subscription model, advertising or product delivered after sale. Because podcast content is often free, podcasting is often classified as a disruptive medium, adverse to the maintenance of traditional revenue models. Podcasting is the preparation and distribution of audio files using RSS feeds to the devices of subscribed users. A podcaster normally buys this service from a podcast hosting company like SoundCloud or Libsyn. Hosting companies then distribute these audio files to streaming services, such as Apple and Spotify, which users can listen to on their smartphones or digital music and multimedia players, like an iPhone. , there are at least 2,999,008 podcasts and 152,596,784 episodes. Production and listening A podcast generator maintains a central list of the files on a server as a web feed that one can access through the Internet. The listener or viewer uses special client application software on a computer or media player, known as a podcast client, which accesses this web feed, checks it for updates, and downloads any new files in the series. This process can be automated to download new files automatically, so it