Rocker arm is part of the valve actuating mechanism. It is responsible for the opening and closing the intake and exhaust valves. Rocker arms are typically in between the pushrod and intake and exhaust valves. They allow the push rods to push up on the rocker arm and push down on the valves. Over the years of rocker arm have been optimized in its designed and material for better performance durability, toughness, high dimensional stability, wear resistance, strength as well as economic factors are the reasons for optimization of rocker arm. This paper review types of rocker arm based on published sources in order to understand rocker arm for its problem identification and further optimization. This paper present what is rocker arm? Where it is used, history related to rocker arm, reason of failure of rocker arm are also discussed in this paper.