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.
Is a video format similar to MP4. The difference between the formats is their developers and protection. Apple company, has developed a format that has provided DRM-lock for M4V. Video files in this format are downloaded from iTunes.