It is a Arduino shield based on L298N H-bridge driver chip.
You can use this shield to drive two DC motors or an four-wire two-phase stepper motor. For power supply , power terminal on board is available – it will also power the Arduino board. Or from the power jack on Arduino board, the shield will get the power form the Vin pin of Arduino and derive the motor using this power.
In many motor and robot project, you need to use the wireless communication, so on board we build a wireless area. Now you can directly put a XBee (or other XBee pins compatible module, like BTBee) and a nRF24l01 module on the board.