Stepper motor

A stepper motor moves in precise, countable increments rather than spinning freely — it advances one fixed 'step' each time you pulse its coils, like the second hand of a clock ticking from mark to mark. Inside, many toothed electromagnet poles surround a toothed rotor; energising the coils in the right sequence pulls the nearest rotor teeth into alignment, nudging the shaft a fixed angle (commonly 1.8°, giving 200 steps per revolution) with every change.

Its magic is open-loop precision: you can command an exact number of steps and the motor obeys, with no position sensor or feedback needed, which is why steppers run 3D printers, scanners, camera lenses, and CNC machines where 'go to this exact spot' matters more than raw speed. The trade-offs are that they hold full current even standing still (so they run warm), they lose torque rapidly at high speed, and if overloaded they 'skip steps' silently — losing track of position with no warning unless you add feedback.