I know that certain springs lower the car, but what do the shocks do??

 

Springs hold the body of the car up. Dampers (the term "shock absorber" is actually a misnomer because dampers don't absorb the "shock" of a bump or pothole- the springs absorb that) control the motion of the springs. Without dampers, the springs would cause the car to bounce constantly. So the dampers stiffen the suspension up as far as small motions go.