A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, known as a fulcrum. It is a rigid bar that can rotate around a point on itself. Levers are used to amplify an input force to provide a greater output force, thereby providing mechanical advantage. The concept of leverage is central to levers, where the output force is greater than the input force. Levers are classified into three types based on the positions of the fulcrum, load, and effort: first-class lever, second-class lever, and third-class lever. The mechanical advantage of a lever is determined by the ratio of the output force to the input force, which is influenced by the distances from the fulcrum to the points where the forces are applied. Levers play a crucial role in various mechanical systems and are fundamental in understanding the principles of force and motion.