um....no. Go read about them if you want to learn more.
well actually it depends what sort of box squat you do.
If you do light touches, then no they dont work any differant muscles than a regular squat to the same depth, with a light touch you basically just go down slowly until you feel the box come in contact then then drive back up.
If you do a pause box squat and you arch hard and then pause on the box sitting in the same position as you are in when descending in the squat for a second or two then explode up then it still doesnt really work many differant muscles, it would just be like doing pause squats but at whatever height the box is at.
But if you land on the box, sit back so your sitting up straight then lean or rock forward and explode up out of the box then yeah, it probably does work differant muscles than if you do a standard free squat. But I also hear it is alot easier to loose your arch and injure your back doing it this way, and it has less of a carry over to your normal free squat.
And in reply to your question to me, I skimmed through your first post and wasnt really paying attention so I didnt realise that it was box squats, I thought you were just doing normal squats, and I read that you said to parallel so I thought they were just standard parallel squats.