A stepper motor is an electric motor that is able to create sharp movements. It is used, for example, in printers. They are also commonly found in robots, automotive devices, and computer hard drives. Like other electric motors, they need an electrical circuit to work. Typically they have more than two wires to control them. There are several versions of stepper motors and several ways to drive them.
DC motors can be considered using two general categories, stepper motors and servo motors.
Servo motors needs a continuous feedback of position to control the state of the motor in order to give the motor specific or desired speed or position. These types of stepper motor are usually more expensive because they required additional circuitry to acquire this constant positional feedback.
The other type of generalized motor is called a stepper motor. This stepper motor is commonly used for simple experiments because it is inexpensive. It doesn't require the position of the motor to be known, hence it won't require additional circuitry. A stepper motor turns to a specific positions in using a constant sequence. This sequence can be achieved in multiple ways.
Full stepping, half stepping, and micro stepping are ways to achieve a sequence of steps from the motor.
Full stepping with a two phase motor calls for two coils to be alternated simultaneously. This form of stepping will allow the motor to spin, but the angle of that spin will be based upon the step angle. The step angle is equal to the 360 degrees divided by the steps per revolutions. The steps per revolutions are found by the number phases on the stator times the number of permanent magnets available to the motor.