A potentiometer is an electrical device used to measure voltage or control electrical devices by varying resistance. It consists of a resistive element and a movable contact, known as a wiper, which slides along the element. By adjusting the position of the wiper, users can change the resistance and, consequently, the voltage output. Potentiometers are commonly found in various applications, such as in volume controls for audio equipment and light dimmers for adjusting brightness. They can also be used in sensors to provide precise measurements in electronic circuits, making them essential components in many devices.