Without proper control, the suspension motion will become excessive and even violent. Enter the shock absorber or damper. If the springs are the heart of the suspension, then shock absorbers can be considered the brains. Shocks use hydraulic friction to damp out or resist suspension motion. That in turn is dissipated into the air.
Shock absorbers work in two directions and are critical as working companions to the springs.
The extension or opening phase is supposed to control the release of spring energy so that the vehicle chassis does not bounce, float or wallow around. The challenge for shock and suspension engineers is designing a shock absorber that provides the correct amount of control for each of a wide variety of suspension actions. Too much control and the vehicle will have a harsh ride and lack traction, too little control and the chassis and tires will bounce around too much. Experience, sophisticated design and quality are necessary to build a good shock absorber.