A cam is a mechanical device that converts rotational motion into linear motion. It typically consists of a rotating disk or cylinder with a specific shape, which pushes against a follower to create movement. Cams are commonly used in engines, machinery, and various mechanical systems to control timing and movement. There are different types of cams, including circular cams, sliding cams, and camshafts. Each type has a unique design that determines how the follower moves. Cams play a crucial role in many applications, such as in automobiles where they help control the opening and closing of engine valves.