Stepper Motors
Stepper motors are used in printers, disk drives, and other devices where precise position control is required. Stepper motors do not turn continuously like DC motors. They move in steps such as 1.8 degreees. There are several types of stepper motors such as unipolar and bipolar.

Identification of step motors
If it has five wires, it's a unipolar only stepper. If it has six or eight wires, it can be used as either. Another way to find out is to open each motor. If the rotor has a number of ridges at some consistent separation angle, and there are no brushes, then you're likely looking at a stepper motor.

Bipolar or unipolar stepper motor:-

Unlike the unipolar stepper motor, the bipolar stepper motor has two leads per phase, neither of which are common. ... Bipolar motors are generally better than unipolar motors. They have more torque and are more efficient. However, they are more complicated to drive because they need reverse current.

Bipolar stepper motor
Bipolar steppers have a single coil per phase and require more complicated control circuitry (typically an H-bridge for each phase). The A4988 has the circuitry necessary to control a bipolar stepper motor. Bipolar stepper motors typically have four leads, two for each coil.

Principle of stepper motor
Working of Permanent Magnet Stepper Motor
The operation of this motor works on the principle that unlike poles attract each other and
like poles repel each other. When the stator windings are excited with a DC supply, it produces magnetic flux and establishes the North and South poles.

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