What is relation between circular motion and oscillation

Dear student 

A point P moving on a circular path with a constant angular velocity ω is undergoing uniform circular motion. Its projection on the x-axis undergoes simple harmonic motion.
The projection of the position of P onto a fixed axis undergoes simple harmonic motion and is analogous to the shadow of the object.
For example, the motion of a pendulum is both oscillatory motion and periodic motion but the motion of the wheels of a car is only periodic because the wheels rotate in a circular motion. Circular motion is only periodic motion and not oscillatory motion