A body is said to be in oscillatory motion when it swings to and fro about a mean position. Ex a swing ,pedulam of a clock
The to-and-fro motion of a body is called oscillatory motion.
Let us consider a string fixed tightly between two walls.
When the string is plucked and released, it executes to-and-fro motion.
All oscillatory motions repeat themselves after regular intervals of time and hence are periodic motions.
Example of Oscillatory Motion:
However, every periodic motion need not be an oscillatory motion. In the oscillatory motion of a body, there is a force that always directs the body towards the position, which is the position of zero displacement. This position is referred to the mean or rest position. This force is the restoring force.