An electromechanical relay is a switch that uses an electromagnetic coil to open or close a circuit. When electricity flows through the coil, it creates a magnetic field that moves a lever or armature, which then either connects or disconnects the electrical contacts. This allows the relay to control larger currents or voltages with a smaller input signal. Relays are commonly used in various applications, including automotive systems, home appliances, and industrial machinery. They provide isolation between the control circuit and the load, enhancing safety and reliability. Additionally, relays can be used for automation and remote control of electrical devices.