Compression Springs are open-coil helical springs wound or constructed to oppose compression along its axis. Helical Compression is the most common metal spring configuration. These coil springs can work independently, though often assembled over a guide rod or fitted inside a hole. When you put a load on a compression coil spring, making it shorter, it pushes back against the load and tries to get back to its original length. Compression springs offer resistance to linear compressing forces (push), and are in fact one of the most efficient energy storage devices available.
This effect shortens the lengths of the spring & stores the energy. Once the pressure is released, the stored energy returns the spring to its original height. Compressions spring is a type of spring that compresses under a load.