Application software describes a loosely defined subclass of software which employs the OS of a computer directly to a task. Typical examples of software applications include word processors, email programs, and media players.

Video and audio exist on a computer as files, and these files use a compression/decompression scheme (codec) to organize the data. These files could be a movie on a DVD, a clip downloaded from a web site, or an MP3. A file holds the data for that particular piece of media but in order to view or hear it you'll need a media player, which is analogous to a set-top DVD player (but capable of far greater versatility). Media players play back many kinds of media files. Common media players are QuickTime, Windows Media Player, RealPlayer, iTunes, and numerous other commercial players and shareware players.