From a macro perspective, a complete stepper motor includes the motor body, motor driver and connecting cables. If you only look at the motor itself, it can be divided into:
1. Motor housing
2. Motor stator
3. Motor rotor
4. Communication interface, etc.

Among them, the rotor can be divided into three parts: rotor 1, rotor 2, and permanent magnet steel. Sometimes there are ball bearings inside to reduce friction and vibration when the rotor is working.
Common stepper motors are all open-loop controlled, that is, they work unilaterally by receiving motion instructions from the controller, and do not feed back information such as speed and position.

In order to improve the working accuracy of the stepper motor, an encoder can be integrated on the stepper motor, and then the speed, position, torque and other information can be fed back in real time, which is convenient for the control correction of the driver.