What is an oscillation?

Oscillation is a type of motion. It is a kind of periodic motion.Contrast with rectilinear motion, the oscilatory motion involves the movement in to and fro directions like a pendulum, vibrating tuning fork or  rocking in a cradle.

An oscillation needs to be understood  in the context of its amplitude, frequency and period of the oscillation.

A simple pendulum  oscillates between two extremes and one complete to and fro motion is called an oscillation. You can take any point in the path of the to and fro movement and observe the direction of the movement.The entire action or movement  of the pendulum  from the point considered to return to the same point and in the same direction is called an oscillation. The pendulum goes to one extreme reverses the movement and goes to another extreme and then reverses the movement and repeats the activity. The single movement (or displacement) of the pendulum from one extreme to another extrme is called the amplitude. Two succesive amplitudes make an oscillation.The time taken for one oscillation (oscillatory movement ) is called a period of oscillation. The number oscillations per second is called the frequency (applies to pendulum, frequency fork or any oscillatory movement). The model of simple pendulum is the most helpful to study oscillations and the study of osillatory movements.