A  brushless ESC  is used to vary the speed of a brushless motor. Controlled by the throttle signal from an RC receiver, the brushless ESC provides variable power to the motor allowing proportional speed adjustments. Unlike a brushed motor, power cannot be directly applied to it. Instead, the speed control intelligently powers each phase of a brushless motor in sequence, causing it to rotate. Brushless speed controls have three motor wires, allowing them to connect to standard three phase brushless motors. A brushed speed control  cannot be used to power a brushless motor.