What is the working mechanism of planetary gearbox?

A ring gear (A) is tightly connected to the gearbox housing, with a sun gear (B) driven by external power at the center of the ring teeth. Between the two, there is a set of planetary gear sets (C) consisting of three gears evenly divided and combined on a tray. The set of planetary gears relies on the output shaft, inner ring gear, and sun gear support to float during this period; When the input side power drives the sun gear, the planetary gearbox can drive the planetary gear to rotate and follow the trajectory of the inner ring gear to revolve around the center. The rotation of the planetary gear drives the output shaft connected to the tray to output power.