It’s simple, really. An automatic watch’s oscillating weight, or rotor, is what winds it up. It does so using the motion of one’s wrist, which actuates the rotor. Which itself is weighted to easily move when the arm moves.
The movement of the rotor is what winds the mainspring. Perpetually, automatically.
In the case of many automatic watches, the rotor’s activity is clearly visible via a see-through case back. But Dior’s Inversé 11½ or Inversé 8¼ calibers were designed to appear on the dial side of the watch.
And in the case of the Dior VIII Grand Bal, this essentially functional component is transformed into a gorgeously decorated focal point of the dial.