Podcasting is the method of distributing multimedia files, such as audio or video programs, over the Internet using syndication feeds, for playback on mobile devices, personal computers and MP3 players. The term Podcasting combines "iPod", and "broadcasting".

Podcast, like 'radio', can mean both the content and the method of delivery. The host or author of a podcast is often called a podcaster.

Though podcasters' web sites may also offer direct download or streaming of their content, a podcast is distinguished from other formats by its ability to be downloaded automatically using software capable of reading feeds like RSS or Atom.

Usually a podcast features one type of 'show', with new episodes released either sporadically or at planned intervals such as daily or weekly. In addition, there are podcast networks that feature multiple shows on the same feed.

The concept of podcasting was suggested as early as 2000 and its technical components were available by 2001, then implemented in the program Radio Userland. In 2003 regular podcasts started showing up on well-known Web sites and software support spread.

By the end of 2004 thousands of podcasts were available, the term had entered widespread use, and Apple Computer had begun to adopt the technology.

Even though the name is a misnomer, in that podcasting doesn't require an iPod and no over-the-air broadcasting is required, it has maintained its prominence in the face of numerous alternatives.

The use of "podcast" to describe both audio and video feeds seemed natural to some users, while others prefer to reserve the word for audio and coin new terms for video subscriptions.

Other "pod-" derived neologisms include "podcasters" for individuals or organizations offering feeds and "podcatchers" for special RSS aggregators with the ability to transfer the files to media player software or hardware.

The "pod" name association came about because Apple Computer's iPod was the digital audio player used by early podcast listeners.

The use of "pod" in 2004 probably played a part in Apple's development of podcasting products and services in 2005, further linking the device and the activity in the news media.

The publish/subscribe model of podcasting is a version of push technology, in that the information provider chooses which files to offer in a feed and you the subscriber chooses among available feed channels.

While you, the user is not "pulling" individual files from the Web, there is a strong "pull" aspect in that you are free to subscribe to (or unsubscribe from) a vast array of channels.

Earlier Internet "push" services (e.g., PointCast) allowed a much more limited selection of content.

Podcasting is an automatic mechanism by which multimedia computer files are transferred from a server to a client, which pulls down XML files containing the Internet addresses of the media files.

In general, these files contain audio or video, but also could be images, text, PDF, or any file type. A podcast is generally analogous to a recorded television or radio series.

The content provider begins by making a file (for example, an MP3 audio file) available on the Internet.

This is usually done by posting the file on a publicly-available webserver; however, BitTorrent trackers also have been used, and it is not technically necessary that the file be publicly accessible.

The only requirement is that the file be accessible through some known URL. This file is often referred to as one episode of a podcast.

The content provider then acknowledges the existence of that file by referencing it in another file known as the feed. The feed is a machine-readable list of the URLs by which episodes of the show may be accessed.

This list is usually published in RSS format (although Atom can also be used), which provides other information, such as publish dates, titles, and accompanying text descriptions of the series and each of its episodes.

The feed may contain entries for all episodes in the series, but is typically limited to a short list of the most recent episodes, as is the case with many news feeds. Standard podcasts consist of a feed from one author.

More recently multiple authors have been able to contribute episodes to a single podcast feed using concepts such as public podcasting and social podcasting.

The content provider posts the feed to a known location on a webserver. (Unlike the episode file itself, the feed is published to a webserver, usually not by other means).

The location at which the feed is posted is expected to be permanent. This location is known as the feed URL. The content provider makes this feed URL known to the intended audience.

You enter this feed URL into a software program called a podcatcher or aggregator (the former term is specific to podcasting while the latter is general to all programs which collect news from feeds). This program retrieves and processes data from the feed URL.

A podcatcher is usually an always-on program which starts when your computer is started and runs in the background. It manages a set of feed URLs added by you and downloads each at a specified interval, such as every two hours.

If the feed data has substantively changed from when it was previously checked (or if the feed was just added to the podcatcher's list), the program determines the location of the most recent item and automatically downloads it to your computer.

Interestingly, it is estimated that perhaps only 20% of podcasts are actually consumed on portable media players; 80% are consumed on the PC onto which they are downloaded.

Some podcatchers, such as iTunes, also automatically make the newly downloaded episodes available on your portable media player. (This is only the typical behavior of a podcatcher; some podcatchers behave—or can be set to behave—differently).

The downloaded episodes can then be played, replayed, or archived as with any other computer file.

Variants of the podcast include the marcast or Podcast Marketing. Podcast Marketing is the method of creating and publishing audio and video programs via the Internet.

It allows a company's or marketer's users, clients, and customers to subscribe to a feed of new information about products and services.

To conserve bandwidth, I suggest you opt to search for content using an online podcast directory.

Some directories allow people to listen online and initially become familiar with the content provided from an RSS Feed before deciding to subscribe and then downloading a huge amount of content, only to find out later that they didn't have any interest.

For most broadband users, bandwidth is generally not a major consideration; however, there are still a number of computers that are connected to the Internet using a dial-up connection.

For comprehensive lists of podcasts, visit podcast directory www.vitalpodcasts.com (opens in new window)