Why need shock absorbers if there are springs???
Springs are the main support in automotive suspension system. However the problem is that springs deflect as the car goes over a bump, then bounce back. The car would continue to bounce up and down if the energy stored in the springs were not dissipated in some way.
See video on car with just springs: https://www.youtube.com/watch?v=rYAMGy9LxVY
That is where shock absorber or dampen comes in.
Shock absorbers takes the energy out of spring and reduces from multiple endless bounces to one bounce. It is an advantage for tire lasting, driver's safety and comfort.
All shock absorbers comes in different length with different fixtures for connecting.
Video on how shock absorber works:
References: