The two categories of brushless motors and controllers are sensored and sensorless. These two categories refer to how the armature location is determined (sensed) and then controlled. A sensored motor (ie Aveox and Novak), you set the motor to a fixed timing to match your specific setup, just as you do with a brushed motor. These motors have small sensors, typically 3 at 120 degree intervals, which determine and communicate the rotational position of the armature. The controllers and motors often need to come from the same manufacture to work correctly. The speed controllers for sensored motors can be less expensive to manufacture since they do not need to perform any motor monitoring. The down side is that the motor is more expensive because it must have the sensors built into it. These sensors can be fragile and they take up valuable space inside the motor. A sensorless motor (ie Hacker, Lerner) is just as its name implies. These motors do not contain any sensors and instead leave the determination of armature position to the speed controller. The Sensorless controllers are more complicated since the controller has to compensate for the lack of sensors in the motor. It does this with added programming and hardware to deal with various magnetic fluxes which occur in BL Motors. Sensorless theoretically allows you to run more efficiently at all throttle settings compared to a sensored setup. | 
The stator or armature is made up of a laminated stack and wound with copper windings. Magnetic sensors detect the angular position of the rotor with respect to the stator. These sensors tell the controller (ESC) which loop needs to have the current on and which ones need the current off. This allows the motor to produce a continuous torque in one direction.