A basic pendulum is made consisting of a reasonably heavy item suspended from fixed support by a string.
In its equilibrium posture, usually hangs vertically.
Oscillatory motion is defined as the to and fro motion of the pendulum in a periodic fashion and the centre point of oscillation is known as the equilibrium position.
The time taken by the pendulum to finish one full oscillation is known as one oscillation.
The distance traveled by the pendulum from the equilibrium position to one side is known as amplitude.
When the bob is shifted out of balance and then released, it begins to vibrate back and forth about its fixed equilibrium point.
The pendulum swing can be called an oscillation motion of a pendulum.