In brushless motors and speed control, you have two different types: SENSORED & SENSORLESS.
Sensored motor as a sensor to help the sensored speed control know the orientation of the motor shaft.
Sensor brushless motor systems always know the position of the rotor, which is especially critical at low speed as well as during the start condition when there is no rotor movement. Sensor brushless motors are often used in applications where starting torque varies greatly or where a high initial torque is required. For the sensorless brushless motor, in contrast, a sensorless speed control does not know the position of the rotor until it is spinning at a certain speed and generating enough back-EMF to calculate its approximate position.