How does metabolism work? let's say I do 1 hour of exercise, do I just burn a few calories or does the exercise make my metabolism faster?

It can raise your metabolism for quite awhile after the exercise.

Both really. Your body uses calories to move so as you're moving you'll burn calories. But when you move or exercise you're muscles your muscles break down and rebuild to contain a healthy amount of fibers. This break down takes energy boosting the amount of calories you burn for a while. But f you choose to exercise again while in this break down you will most likely fatigue fast or overwork yourself. This is why propel have rest days