powerlifters do a lot of triples, doubles, and singles along with speed work, use of chains, and bands to work for the explosive power. they do box squats of various heights to strengthen their squats in certain areas to help gain that explosiveness. pretty much all of powerlifting is optimizing form to become more explosive and strong. they don't care what they look like, at least most of them it seems anyways.
powerlifting focused mainly on their three lifts: deadlift, squat, and bench. any other work they do is to strengthen these lifts in some way.
mass building obvious focuses on getting a symmetrical look and a big look for some. so you're going to basically do those 3 fundamental lifts as well, but you add the extra lifts that work best for your physique.