An M3U file is a media playlist file supported by several media players such as Winamp and iTunes. It contains a playlist of MP3s and other audio or video files and lists the locations of media files in a plain text format.
M3U playlists are typically used for audio playlists, but some may also include references to video files. M3U files contains references to media files, but not the actual files themselves.
NOTE: "M3U" is short for "MP3 URL" or "Moving Picture Experts Group Audio Layer 3 Uniform Resource Locator."