Write the difference between periodic and simple harmonic motion.

(N/A) $1$. Periodic Motion: Any motion that repeats itself at regular intervals of time is called periodic motion. It does not necessarily require a restoring force proportional to displacement. Example: The motion of the Earth around the Sun.
$2$. Simple Harmonic Motion $(SHM)$: It is a special type of periodic motion where the restoring force is directly proportional to the displacement from the mean position and is directed towards the mean position. The equation of motion is given by $F = -kx$,where $k$ is the force constant and $x$ is the displacement. Example: The motion of a simple pendulum for small amplitudes.