Collision is known as the sudden but short interaction of two or more than two bodies to exert a mutual influence, usually by exchanging energy. For example, two biliard balls, a hammer and a nail etc.

There are three types of collision, Perfectly elastic, Partially elastic and Perfectly inelastic.
In perfectly elastic collision, two bodies bounces off without any loss in kinetic energy or momentum, for example: a hard cricket ball hitting a hard surface.
In partially elastic collision kinetic energy is not conserved but momentum is, for example: a soft tennis ball hitting a hard surface. And in perfectly inelastic collision, the bodies stick together and moves at a common speed, as the momentum is conserved but kinetic energy is lost, for example: when a ball of clay is dropped.