DC motor is a continuous rotation motors, it only has two wires. This motor will work when you give it the power no matter what, and it will stop when you remove the power.
The position of servo motors can be controlled more precisely than those of standard DC motors, and they usually have three wires (power, ground & control).Power to servo motors is constantly applied, with the servo control circuit regulating the draw to drive the motor. Servo motors are designed for more specific tasks where position needs to be defined accurately.
A stepper motor is essentially a servo motor that uses a different method of motorisation. Where a servo motor uses a continuous rotation DC motor and integrated controller circuit, stepper motors utilise multiple toothed electromagnets arranged around a central gear to define position.
I use the potentiometer to control the servo motor rotates, when you give more power to the servo motor, the motor with move faster. I think it can use in the children electronic toy, as a parent, they can control the toy move or stop.
-Arduino + USB Cable