A compound bow is a modern bow

Bow (weapon)

The bow and arrow is a projectile weapon system that predates recorded history and is common to most cultures.-Description:A bow is a flexible arc that shoots aerodynamic projectiles by means of elastic energy. Essentially, the bow is a form of spring powered by a string or cord...

 that uses a levering system, usually of cables and pulley

Pulley

A pulley, also called a sheave or a drum, is a mechanism composed of a wheel on an axle or shaft that may have a groove between two flanges around its circumference. A rope, cable, belt, or chain usually runs over the wheel and inside the groove, if present...

s, to bend the limbs.

The limbs of a compound bow are much stiffer than those of a recurve bow

Recurve bow

In archery, the shape of the bow is usually taken to be the view from the side. It is the product of the complex relationship of material stresses, designed by a bowyer...

 or longbow

Longbow

A longbow is a type of bow that is tall ; this will allow its user a fairly long draw, at least to the jaw....

. This limb stiffness makes the compound bow more energy-efficient than other bows, in conjunction with the pulley/cams. The compound bow has its string applied to pulleys (cams), and one or both of the pulleys have one or more cables attached to the opposite limb.