HowStuffWorks explains that levers work by reducing the force needed to move weights. They achieve this by increasing the distance through which the required force acts. For instance, a 1-kilogram force that acts through a distance of 3 meters is capable of moving a 3-kilogram weight in 1 meter, if friction is ignored.
HowStuffWorks states that levers overcome a resistance when force is applied, and they are used to gain force and speed or change direction. They have a fixed support to which they freely turn about called the fulcrum. In some levers, it is possible to increase speed by applying the force over a shorter distance than the resistance is moved. A proportional increase of force is needed for this. Examples of levers include seesaws, crowbars, wheelbarrows, wrenches, nutcrackers, bats, hammers and balance scales. Body parts, such as the hands, arms, legs and feet, also function as levers.
Professor Odis Hayden Griffin published on AutoCWW Colorado that physicists categorize the lever as one of the four simple machines used to perform work. When distances between the load and the fulcrum and between the force and the fulcrum are varied, a person needs a lesser amount of effort to move a heavy load. By reducing the force necessary to move a load, levers make work easier.