A relay is an electrically operated switch that allows a low-power signal to control a higher-power circuit. A 30A Power Relay, specifically, is designed to handle electrical currents up to 30 amperes (A), making it suitable for high-power applications. It uses an electromagnetic mechanism to open or close the relay's contacts, allowing it to switch large amounts of electrical power on and off without any direct manual intervention. Typically, these relays are controlled by a smaller control circuit, which in turn triggers the relay to activate heavy-duty electrical devices.