Some special types of applications of the electrical motor where rotation of the motor is required for just a certain angle not continuously for long period of time.
The motor is required with some special arrangement which makes the motor to rotate at a certain angle for a given electrical input (signal).
Servo motor uses a servo mechanism.
It is a closed-loop mechanism that uses position feedback to control the precise angular position of the shaft.
Servo motors have three wires.
Two of them are red and black which is used to give power to the motor.
The third wire is used to provide a control signal for an angular position.
It uses Pulse Width Modulated (PWM) waves as control signals.
The angle of rotation is determined by the width of the pulse at the control pin.
import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM) //BCM is broadcom which specifies the actual pin number considered by broadcom chip
GPIO.setwarnings(False) //Ignore warnings
p = GPIO.PWM(Servo_pin, 50)
p.ChangeDutyCycle(7.5) //turn towards 90 degree
p.ChangeDutyCycle(2.5) // turn towards 0 degree
p.ChangeDutyCycle(12.5) // turn towards 180 degree