Shock Absorbers and Coilovers are two identical subject that address the same issue, to minimise the shock. A shock absorber or damper is a mechanical or hydraulic device designed to absorb and damp shock impulses.
Coilover actually a combination of shock absorber and housing of coil spring as a single unit to dampen the shock from ground before transferring to vehicle. Shock Absorbers and Coilovers have the same function that are to cushion the impact from roads or terrains to the driver.
Shock Absorbers and Coilovers come from different brands and with own engineering enhancement to cater for a special track conditions as well as for an efficient street drive.
Should you encounter any bumping issues or any squeak sound unnecessary come from suspension area then among the first item to check is the absorber or coilover.