Difference between simple pendulum and compound pendulum?

Pendulums are a combination of certain materials which displays periodic oscillatory motions. 

A simple pendulum is the simplest form of the pendulum, which we are more familiar with, whereas the compound pendulum is an extended form of the simple pendulum.

SIMPLE PENDULUM

An ideal simple pendulum consists of a heavy point mass body(also called as bob) suspended by a inextensible, weightless & perfectly flexible string from a rigid support about which it oscillate. But an ideal pendulum is impossible to construct.

Here, time period is the dependent on the length and acceleration due to gravity. Considering acceleration due to gravity as constant we can say then the time period depends on the length of the pendulum

COMPOUND PENDULUM

Any rigid body suspended from any fixed support constitutes a physical pendulum. The body can have any irregular shape. 

Here, the length is replaced by effective length  i.e. Effective length of the pendulum= distance between the suspension point and centre of mass.

The basic difference lies in the Mass that each pendulum consists. Due to irregular masses, a compound pendulum came into existence.