The Motor Shield is based on the Liberty 298 H-Bridge, which is a dual full-bridge driver. Allows you to drive inductive loads such as relays, solenoids, DC and stepper motors. Available measurements of motor current.
Power supply 5V - 12V
IC: L298P, Can be connected 2 DC motors or 1 stepper motor
Max current 2A per channel or 4A max (with external power source)
More information here: http://arduino.cc/en/Main/ArduinoMotorShieldR3