What does the term "movement" refer to in horology?

In horology, the term "movement" specifically refers to the inner workings of a watch, which includes all the components that contribute to the timekeeping function. This encompasses the mechanism that drives the watch's time display, including gears, springs, and other essential parts that work together to keep accurate time.

Understanding the movement is crucial for both watchmakers and collectors because it determines not only the accuracy of the watch but also its complexity and craftsmanship. Movements can vary widely, from simple quartz movements to intricate mechanical movements with numerous complications.

The other options touch on other aspects of a watch but do not accurately define what is meant by "movement." The external design pertains to the watch's casing and appearance, the method of powering the watch relates to how its energy is generated and utilized, and the winding mechanism is just one part of the movement responsible for recharging mechanical watches. Therefore, the correct choice emphasizes the comprehensive system that forms the very heart of a watch's functionality.