MOV/.mov is a video Container format for QuickTime.
The multimedia container file can hold multiple tracks, audio, video, effects or text files. Each Track, regardless of type, has its own digitally-encoded media stream using a specific Codec.
QuickTime natively supports AIFF, WAV, DV, MP3, and MPEG-1. Including extensions, QT can also support Ogg, ASF, FLV, MKV, and DivX Media Format.
MP4 was based on Apples MOV (Quicktime) container, which they were already using for MPEG-4 content. Rather than using a different type of file for elementary (separate video and audio) streams, MOV and MP4 use the same container regardless of how many or what type of streams are stored in it. Apple's iTunes online music store made audio only MP4 files a common site for consumers. Although not all portable media players can read them, Apple's M4A extension (for audio only MP4 files) has become anonymous with audio.