Effect of damping (friction) on motion

There are three cases illustrated to the left :

1. No friction (SHM).
2. Underdamped SHM (some friction, but still oscillates).
3. Overdamped (friction - no oscillation, just returns to origin).

With no friction, the mass will oscillate "forever". With the underdamped SHM case, there is some friction, but it continue to oscillate (that is, go past the origin to the other side). With the overdamped case, there is enough friction to keep the mass from passing to the other side .. it will just "relax" toward the origin.