Relays are electrical switches that allow a low-power control signal to activate or deactivate a much higher power circuit. They are used to control various devices, such as motors, lights, alarms, and many other systems. Relays come in different types, including mechanical (electromechanical) relays and solid-state relays (SSRs). Electromechanical relays consist of an electromagnet and a set of contacts, which physically open or close when the coil is energized. In contrast, solid-state relays use semiconductor materials to perform the same switching function without any moving parts, making them more reliable and faster.