Paveway IV is actually a kit that is attached to an unguided bomb. The 50.5 kg (111 pound) Paveway kit contains guidance electronics, computers, and battery powered winglets. But to work the carrying aircraft must have a fire control system that enables the pilot to get the GPS data (received from troops on the ground) into the Paveway IV equipped bomb.
Once attached to a one ton, half ton, or quarter ton bomb, the Paveway IV can achieve precise (within a meter or less) accuracy using a laser designator. Now there is also GPS guidance to land within ten meters (31 feet) of the aiming point. The U.S. firm that manufactures the Paveway bombs, Raytheon, has produced over 250,000 kits so far, of which about twenty percent have been used in combat with great success.
Earlier versions of Paveway did not have GPS. Most just only had laser guidance. Britain has since added GPS to Paveway IV. While more accurate, laser guidance requires that someone on the ground or in the air be shining a laser on the target. The Paveway then homes in on the reflected laser light (of a particular frequency). GPS guided bombs can hit the target under bad weather conditions and only have to worry about jamming of the GPS satellite signal.