A Contact Relay is an electromechanical switch used to control a circuit by a low-power signal or to manage multiple circuits with a single signal. It consists of a coil that generates a magnetic field when energized, causing a set of contacts to open or close, thus allowing or interrupting the flow of electricity. These relays are commonly used in various applications, including automotive systems, industrial machinery, and home appliances. They help in isolating different parts of a system, ensuring safety and efficiency by preventing high voltages from affecting sensitive components.