What is a WAV file

WAV is a Microsoft and IBM standard for storing audio on PCs. It is a variant of the bitstream type RIFF and is therefore very close to the audio types IFF and AIFF, which are used on Apple Macintosh computers.

Source: Wikipedia

If you are going to upload music for a digital release, you do this in the .WAV format.

It is the most popular file format of musicians and other music professionals in the music industry because you have little to no loss on the sound quality.