Rocker arms are essential components of an internal combustion engine's valvetrain system. They transfer the camshaft's rotational motion to the valves, opening and closing them at precise intervals. When choosing rocker arms for your engine, consider material, ratio, and adjustability. Material options include stamped steel for stock applications, or lightweight aluminum for high-performance engines. Rocker arm ratio affects valve lift, and adjustable rocker arms allow for fine-tuning valve timing.