MP4 is a digital multimedia container format that is commonly used to store video and audio, but it can also be used to store other data such as subtitles and still images. It is a highly versatile and compressed video format that can store a lot of video and audio information in a smaller file size. Here are some key features of MP4 format:

• File extension: The only filename extension for MPEG-4 Part 14 files as defined by the specification is .mp4, but it can also have other extensions such as .m4a, .m4p, .m4b, .m4r, and .m4v.
• Compatibility: MP4 is widely accepted and can be used on multiple platforms such as TVs, mobile phones, computers, multimedia software, and web browsers.
• Compression: MP4 has a high amount of compression, resulting in smaller file sizes.
• Metadata: MP4 allows you to attach metadata to your files, indicating the flags for timestamps, random access, and so forth.
• Media data: The data in an MP4 file is mainly divided into two segments – media data and metadata. The media data includes streams of video, audio, and subtitles.

MP4 is a "lossy" compression format, meaning file information is lost during compression. While MP4 files can play audio, they shouldnt be confused with M4A and MP3, as these are file formats that only contain audio. If youre a video editor looking for a small final file size that allows for easier digital distribution (like streaming) on many platforms, an MP4 may be the perfect format for you. However, if youre looking for lossless compression or high file security, this format may not be for you.