The Grove - 4-Channel SPDT Relay has two single pole - double throw (SPDT) switches. It only requires low-voltage and low current signals to control those switches. Specifically, you can use 5V DC to control max.250V AC or 110V DC.
An on-board STM32F030F4P6 is used to control the channels separately. The control command is transmitted via the I2C interface. The on-board STM32F030F4P6 will parse the command, so that you can control the switch you want.
The Relay is a digital normally open switch that controls a relay capable of switching much higher voltages and currents than your normal Arduino boards. When set to HIGH, the LED will light up and the relay will close allowing current to flow. The peak v