The answer is a multi-touch interface.
A multi-touch interface makes it possible for a touchscreen to sense input from two or more than two points of contact at the same time. This type of technology allows you to use multiple finger gestures to do things like spread your fingers to zoom out, pinch to zoom in, or rotate your fingers to rotate an image. An example of a multi-touch design is the large wall-mounted screen that you see on CNN. The size of these screens can measure from four feet by six feet or more.