For some reason in some mixes, like a PVD mix I have heard before has raised a question of thought for me to ask.

In example, in some of the mixes, the tracks sometimes have this filtered sound to it, it almost sounds like the volume is in balance with all the other tracks and there are slight modification to the sound.

When I listen to the unmixed version of the track, it sounds a bit more plain. The unmixed versions doesn't have that warm amp'd sound that the mixes created by some DJs do. is there a reason why people do this, and what is it called? Someone once told me it was remastering but I wasn't sure if remaster fits the description