MP4 format is short for MPEG-4 Part 14 that was developed by Apple in 1993. From a technical point of view, it is a media container that was designed as a video format. Such a file may contain video, audio, static images, subtitles, and text within it. Also, MP4 files may contain data defined by the standard, such as file creation time, duration, title and album cover, language code of the stream, the legal status of the work, etc.
In this case, the container itself does not implement any encoding. It only contains files in certain formats. Therefore, to play them, you need to have a player or codecs that support these formats. MP4 is widely used on the Internet for embedding video in web pages because it gives developers and users the necessary width of opportunities and optimal download speed.
At the moment, MP4 is one of the most popular video formats that are used on the Internet and not only, therefore converting MOV to MP4 is a very popular service.