WAV is audio with nothing taken away: every sample intact, every megabyte accounted for. It was born in 1991, Microsoft and IBM, and its real weak spot is being carried around: it refuses to shrink.
FLAC is the audiophile's handshake: CD-perfect sound at roughly half the shelf space. Free Lossless Audio Codec: think ZIP for sound: it decompresses back to the exact original. That makes it the right destination when what you need is archiving music with zero quality loss and a genuine size saving.