Is a media container format designed for streaming over the Internet. Used on popular video hosting sites. Video is usually stored in h.263 and h.264 formats, audio is a in MP3 or other less popular codecs. FLV-file format is a bit stream, which provides high-quality image even at low bit rates.
this is a lossless-format (and encoding algorithm) for Apple platforms. M4A is widely used in iPod players and as a component in QuickTime media-players. The m4a codecs decoder is found in open sources - this allows third party users to open files in that format.