Pulse-width modulation (PWM) is a technique used to control the amount of power delivered to electrical devices. It works by varying the width of the pulses in a signal while keeping the frequency constant. By changing the duration of the "on" time versus the "off" time within each cycle, PWM can effectively adjust the average voltage and power supplied to devices like motors and lights. This method is commonly used in applications such as LED dimming and DC motor speed control. PWM is efficient because it minimizes energy loss, allowing devices to operate smoothly while consuming less power compared to traditional methods of voltage regulation.