Whats the deference between "Displacement on-demande" and "active-fuel management"?

Active Fuel Management (formerly known as Displacement on Demand) is a trademarked name for the automobile variable displacement technology from General Motors. It allows a V6 or V8 engine to "turn off" half of the cylinders under light-load conditions to improve fuel economy. Estimated performance on EPA tests show a 5.5%-7.5% improvement in fuel economy