Machines are often used to make work easier, by lowering the force needed to do a particular job. All more complex mechanical machines make use of the various simple machines described on these pages.
Historically, the lever was probably the first simple machine to be discovered by man, since a simple stick used to pry insects out of bark is a primitive lever; chimpanzees and even some birds make use of this. The next simple machine to be discovered by humans was probably the wedge, in the form of a sharp rock or bone used to make arrowheads and knives, millions of years ago. Since then, we have learned to use the inclined plane, or ramp, to lift heavy weights upwards, when we built the pyramids; later discoveries included the screw, which Archimedes put to use to pump water, the pulley, and the wheel & axle.
All of these simple devices use the principle of spreading force over distance: if you push further, you can use less force.