What is cerebellum ? What happens when it is injured ?

Cerebellum is the second largest part of the brain. It lies in behind the cerebrum and above medulla oblongata in human body. 

When cerebellum gets injured the voluntary movement that is intended movement of the body gets affected. 

Coordination of voluntary movements. Most movements are composed of a number of different muscle groups acting together in a temporally coordinated fashion. One major function of the cerebellum is to coordinate the timing and force of these different muscle groups to produce fluid limb or body movements.

Even though the cerebellum has so many neurons and takes up so much space, it is possible to survive without it, and a few people have.  There are nine known cases of cerebellar agenesis, a condition where this structure never develops.

Damage to the cerebellum can lead to: loss of coordination of motor movement , the inability to judge distance and when to stop ,  the inability to perform rapid alternating movements ,  movement tremors , staggering, wide based walking.