A watch that winds itself by your wrist’s motion? It may sound a little confusing.
The movement of your wrist and body causes the rotor (a metal weight attached to a winding mechanism) to pivot freely on its staff in the center of the movement.
The rotor rotates back and forth in a circular motion at the slightest action of your wrist. The rotor’s movement then winds the mainspring.
A mainspring is a flat coiled spring that provides power to automatic watches.
In order to provide a comparison, check out a hand-wound watch. These type of watches take more effort because the wearer must wind the watch by turning the crown.