A lever is a simple machine consisting of a rigid beam balanced upon a fixed hinge known as a fulcrum. A force applied to one end of the beam is multiplied in proportion of the length of the beam from that end to the fulcrum to the length of the beam of the other end to the fulcrum.

The distinguishing characteristic of a lever is that it multiplies force without requiring more energy.

When we talk about leverage in business, this is what we mean: multiplying efficacy without requiring more work.