When we buy a stepper motor, we often see how many phases does this stepper motor have, what does this phase mean here?
The so-called phase is how many pairs of energized windings the stator inside the motor has. For the most common two-phase stepper motor, it has four energized windings inside, that is, two pairs, and it is called a two-phase stepper motor.
When stepping and energizing, the two windings of each phase are a magnetic pole N and a magnetic pole S.

Because the motor rotor is also half N and half S, it will move according to the principle that like poles repel and opposite poles attract each other.
If we electrify the two phases in turn, the phenomenon that the rotor will continuously follow the rotating magnetic field of the stator will occur.
If we change the current direction of the energized winding, the rotor will move in the opposite direction, and the stepper motor will reverse.
In addition to the most common two-phase stepping motor, there are also three-phase stepping motors, four-phase stepping motors, five-phase stepping motors, etc., which are suitable for more demanding motor usage scenarios.