Remember when you were a kid and had to get a haircut? They tried to get you in and out as fast as possible and the last thing they wanted was to dunk an already screaming kid's head into water, so proper hair washing was out. Dry hair is difficult to cut, so out came the spray bottle full of water. This uses a mechanical pump to force the water through a nozzle that atomizes the stream. It controls the amount of liquid applied, so things can be slightly wet instead of soaking. Those spray bottles are dampeners; the things in your car are dampers.
There's some confusion as to the point of dampers, whether in the form of shock absorbers, struts or even rotational dampers. Their function is often confused with that of springs. While they operate within the same system, they have a much different purpose.
As with most things, looking at units of measurement first will give some idea of what they do. A spring is rated in force per displacement: pounds per inch, kilograms per millimeter, etc. If a spring rated at 400 pounds/inch is subjected to a 400-pound force, it compresses one inch. If that force is 800 pounds, it will compress two inches.
A damper is measured in force per velocity. Americans generally rate a shock in pounds per inches per second. The pound is the force and the inches per second is the velocity. Imagine a shock absorber rated at 200 pounds per inch per second. When a 200-pound force is applied, it will take one second to move one inch. With the application of a 400-pound force, it will move two inches in one second, or one inch in half a second (both examples assume linear rates in both the spring and the shock).
The springs on a car determine ride height and keep it from dragging on the ground. Dampers, on the other hand, would not hold a car up.
So if springs support a car, why bother with shocks at all? Springs have a natural frequency. They will oscillate, or bounce, at that frequency whenever energy is put into them. Hitting a bump or any car body movement would result in energy being applied to the spring. Friction in the suspension pivots and air resistance would be the only things that would dissipate that energy. A shock absorber, on the other hand, damps the motion by creating friction. The energy in the spring is absorbed by the shock, converting kinetic energy (motion) into heat energy.
Controlling how fast the suspension moves is not only useful for a car's ride. Suspension tuners take advantage of damping rates to change handling characteristics. With stiffer damping rates, a tuner can control the roll rate of a vehicle's body, which in turn affects weight transfer. This is not only important when entering a corner and the suspension is loaded up-or compressed-but equally important when the suspension is unloaded (rebound). It would be quite unsettling to exit a turn and have the car suddenly spring straight back up. Tuners aim to keep everything moving smoothly and controlled.