What is difference between Stepper motor and Servomotor?

Answer 1

A stepper motor is a motor that does not run at a "constant speed". It turns by a certain angle at each "step". It will jump steps of 5, 7.5, 10 etc degrees at each impulsion
They are used to position things with precision, ie. they drive a lead screw on which a chariot is mounted. Depending on the step angle and the screw, we count the pulses to send to advance the chariot over a precise distance.
A servo motor is a DC motor with a feedback loop (usually a potentiometer mounter on the haft of the motor, or a "shaft encoder"). A signal is applied to the servo as the final position. The servo then turns the motor until the output of the potentiometer equals the input signal.
(It is much more complex than that, but this is a short answer).