One of the feature of notebook is capability to extend the screen into external device, like second monitor or even huge large screen via projector. To turn on this feature, user need to do some press of button combination shortcut. For the latest notebook can done with the software side.
Every brands of notebook or laptop has their own button combination to turn this capability. Commonly, their using combination between Fn button with Fx button. Fn means Function button, where Fx are F1 - F12 button. Normally, Fn button is located at the lower row of keyboard, and F1 - F12 are at the top of keyboard.