A relay is an electrical device that acts as a switch, allowing a low-power signal to control a higher-power circuit. It consists of an electromagnet, a set of contacts, and a spring. When electricity flows through the electromagnet, it creates a magnetic field that moves the contacts, either opening or closing the circuit. This enables the relay to control larger devices, such as motors or lights, without needing a direct connection. Relays are commonly used in various applications, including automobiles, home appliances, and industrial machinery. They help protect sensitive components from high voltages and currents, ensuring safe and efficient operation of electrical systems.