A lever is classified as a type of simple machine that amplifies an input force to lift or move a load. It consists of a rigid beam, a fulcrum (pivot point), and a load (object being moved). Levers can be categorized into three classes based on the relative positions of the fulcrum, load, and effort applied. They are used in a variety of applications, from everyday tools like seesaws to complex machinery. Understanding levers is essential in physics and engineering for designing systems that require force multiplication or direction change.