A lever is a simple machine consisting of a rigid bar that pivots around a fixed point, known as the fulcrum. This mechanism is designed to amplify force or distance through the application of mechanical advantage. The function of a lever depends on the relative positioning of three forces: the effort, the load (or resistance), and the fulcrum. By changing the ratio of the effort arm's length to the load arm's length, the magnitude of the output force can be controlled. This principle allows for the movement of heavy loads using smaller amounts of applied force, making it a foundational concept in engineering and physics that describes how forces are efficiently transmitted and multiplied.