What is MP4 Video?

As one of the most popular video formats these days, mp4 is compatible with a wide range of video devices. However, do you ever have an idea what exactly it is?

Firstly, it'll be necessary to give a brief introduction of MPEG-4. MPEG-4 is a method of defining compression of audio and visual (AV) digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG) (ISO/IEC JTC1/SC29/WG11) under the formal standard ISO/IEC 14496 – Coding of audio-visual objects. Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice (telephone, videophone) and broadcast television applications.

MPEG-4 consists of several standards—termed "parts"and MP4 is just Part 14 of it.

MPEG-4 Part 14 or MP4 (formally ISO/IEC 14496-14:2003) is a multimedia container format standard specified as a part of MPEG-4. It is most commonly used to store digital video and digital audio streams, especially those defined by MPEG, but can also be used to store other data such as subtitles and still images. Like most modern container formats, MPEG-4 Part 14 allows streaming over the Internet. A separate hint track is used to include streaming information in the file. The only official filename extension for MPEG-4 Part 14 files is .mp4.

Some devices advertised as "MP4 Players" are simply MP3 Players that also play AMV video or some other video format, and do not necessarily play the MPEG-4 part 14 format.

MP4 files can also be played back on Windows Media Player, Apple QuickTime Player, Winamp, Real Network’s Real Player 10, foobar2000, or any other player that supports MPEG-4.
From wikipedia