Grove – MOSFET enables you to control higher voltage project, like 15VDC, with low voltage, say 5V, on microcontroller. A MOSFET is a kind of switch, but its switching frequency can reach up to 5MHz, much faster than normal mechanical relay. There are two screw terminals on the board. One for outer power source and the other for device you want to control. Grove – MOSFET will pass the power from one end to another when closed. But if outer power source is absent, your device can still draw power from microcontroller via the Grove interface.