Question

what is tha reastoring force

Answer 1

The force you apply to spring which compress that is restoring force.

Answer 2

Restoring force, in a physics context, is a force that gives rise to an equilibrium in a physical system. If the system is perturbed away from the equilibrium, the restoring force will tend to bring the system back toward equilibrium. The restoring force is a function only of position of the mass or particle.