Adding external power to the motorshield

[system]

Arduino motor/stepper/servo control - How to use

---

If you would like to have 2 seperate DC power supplies for the Arduino and motors. Plug in the supply for the Arduino into the DC jack, and connect the motor supply to the PWR_EXT block. Make sure the jumper is removed from the motor shield.
That's a quote from the page - replete with misspelling and sentence fragment.

Ok thank you? Sorry for the noob quetion, but what is the jumper?