A lever arm is the distance from the pivot point, or fulcrum, to the point where force is applied in a lever system. It plays a crucial role in determining how much mechanical advantage a lever provides. The longer the lever arm, the less force is needed to lift a load, making tasks easier. In physics, the concept of a lever arm is essential for understanding torque, which is the rotational force around a pivot. For example, in a seesaw, the distance from the center to where a person sits represents the lever arm. This distance affects how easily one side can lift the other.