The MOV extension designates whether a file is usable on a particular operating system or not. These can be Mac OS or a PC on Windows. However the extension like MOV can also display a file which was started on one computer but is playable on another. MOV extension represents QuickTime video that is a standard format used by MAC computers.
MOV was developed by Apple for making, viewing and distributing multimedia files that can contain animations, video, audio and content related to virtual reality. MOV can store tracks of data. Each file may hold digital media stream or reference to another stream in a different file. This way you can edit them quite easily without the need of rewriting data after editing. MOV videos take 4-20 MB of space per minute which is more than RM or Real Media files. Another major advantage of MOV files is that both Mac and Windows versions of the Apple's QuickTime player can open them. And also the third-party players such as RealPlayer can run the MOV format on both these platforms.
MP4 is an extension used for the files of MPEG 4 format and support video.
MOV extension is a standard video format for the Apple's QuickTime player and the MP4 file structure is the basis of Apple's QuickTime technology. MAC users might want to convert MOV to MP4 for storing them on their hard disks or for uploading them to video websites such as YouTube or Google. This is so because MP4 files typically get more compressed than the MOV ones. But remember it may cause a loss in quality due to the compression standards.