springs are what give a car a smooth ride...but without the shocks the car continues to bounce....when a shock compresses you want it to move quickly at first & the get greater resistance to movement as it compresses to smooth out the "bump"...the shock then needs to get back to where it was at the fastest possible time to absorbe the next "bump"
without going past the neutral position.so it must have low reasistance to movement at first & increase in resistance( Rebound) as it nears the neutral position