The forward clutch drives the sun gear in the planetary gearset.

Yes, that's correct. In an automatic transmission, the forward clutch is engaged to drive the sun gear of the planetary gearset. This allows power to be transmitted from the engine to the wheels, enabling the vehicle to move forward. The planetary gearset, which consists of the sun gear, planet gears, and ring gear, is responsible for changing the gear ratios and thus the speed of the vehicle.