In physics, simple harmonic motion refers to repetitive oscillation back and forth through a central or equilibrium position. A pendulum is a good example of a physical system that exhibits simple harmonic motion. The time taken to complete one full oscillation is called a time period.
In simple harmonic motion, the time interval of each oscillation is the same because the maximum displacement on one side of the central position is equal to the displacement on the other side of the equilibrium position. The force that is responsible for the motion is directly proportional to the distance from the equilibrium position, and it is always directed towards the central position.