A stepper driver, or stepper motor driver, is an electronic device used to control and power stepper motors. It translates control signals from a computer or controller into precise movements of the motor. Stepper drivers generate the necessary current and voltage to energize the motor's coils in a sequence, allowing for incremental and accurate rotation. They offer features like microstepping for finer control, protection circuits, and different drive modes, making them crucial in applications like 3D printers, CNC machines, and robotics.