The difference is the energy source of the watch and its mode of operation:A quartz watch uses an electronic movement, powered by a battery. When the stack is empty, the watch stops.An automatic watch uses a mechanical movement, made of a series of wheels and springs. To function, the watch uses the energy that you release when you move the wrist or when you turn the crown of the watch (hand winding).Our automatic watches generally have a 40H power reserve: fully charged, they can continue to operate 40 hours without being worn.More details on differences between quartz and automatichere.