An electromagnetic relay is an electrical switch that uses an electromagnet to control the opening and closing of contacts. When an electric current flows through the coil of the relay, it generates a magnetic field that attracts a movable armature, either closing or opening the circuit connected to the relay. This allows a low-power signal to control a higher-power circuit safely. These relays are commonly used in various applications, including automotive systems, industrial machinery, and home appliances. They provide isolation between the control circuit and the load, enhancing safety and reliability in electrical systems.