FLV

(Flash Video). FLV files have a .flv file extension and are either used from within .swf files or played through a flv aware player, such as VLC, or QuickTime and Windows Media Player with external codecs added.
Flash Video is a file format used to deliver video over the Internet using Adobe Flash Player (initially produced by Macromedia) versions 6–10. Until version 9 update 2 of the Flash Player, Flash Video referred to a proprietary file format, having the extension FLV. The most recent public release of Flash Player supports H.264 video and HE-AAC audio. Flash Video content may also be embedded within SWF files. Notable users of the Flash Video format include YouTube, Google Video, Yahoo! Video, Reuters.com, metacafe, and many other news providers.

The format has quickly established itself as the format of choice for embedded video on the web. For instance, the standards documentation for BBC Online deprecates the use of other formats previously in use on its sites[1] such as RealVideo or WMV.