ALL OSCILLATORY MOTIONS ARE PERIODIC. PLEASE EXPLAIN WITH EXAMPLE .

Yes it is correct that all oscillatory motions are periodic motions but it is not correct that all periodic motions are oscillatory motions. 

The reason behind this is that::

Oscillatory motion is the to and fro motion motion. 

E. G. Pendulum. 

It is periodic motion because it repeats after fixed interval of time. 

As same all oscillatory motions are periodic motions. 

But if we take a example of period motion like earth revolves rhe sun. 

It is a periodic motion bcoz it is repeated after a fixed interval of time means earth completes its revolution Around the sun in 365and 1/4 days.but it is not oscillatory motion bcoz earth is not acquiring to and fro motion.