Definition - What does MP4 mean?
MP4 is a file format created by the Moving Picture Experts Group (MPEG) as a multimedia container format designed to store audiovisual data. The MP4 is largely replacing earlier multimedia file formats, and creating some changes in the way that vendors sell audiovisual files to the public.
Techopedia explains MP4
The MP4 is based on a QuickTime file format, and has various file name extensions that can help provide clues to what kind of content is contained in the file. This has led to some confusion on the part of users over just what an MP4 is and how a particular MP4 is set up. Experts point out that some MP4 files are encrypted with what’s called Fairplay Digital Rights Management, which is a technology used by Apple to protect some of the content that it sells on the iTunes platform.
A quick history of the MP4 and Fairplay technology reveals that while Apple did use Fairplay encryption on songs, the company currently sells songs without Fairplay encryption in the United States. However, some other kinds of audio files may be encrypted. Common extensions include .mp4, which is commonly used for audiovisual files, .m4a, which is often used for non-protected content, and m4p, which can indicate that the file is protected by Fairplay encryption. The use of Fairplay encryption has led to a number of freeware offerings aimed at decrypting Fairplay. However, the greater issue is whether audiovisual file vendors will continue to maintain a hybrid strategy of encrypting some files while not encrypting others.