Computer Hardware


Under the surface of a touchscreen there are 3 layers. The resistant, the capacitive and the surface acoustic wave. They are all held apart by tiny spacers, so that when you touch, they all meet and send signals through tiny wires to the "brain" of the device.
iPhone/iPod Touchscreens Explained

A scratch resistant layer is placed on top to protect the touchscreen.

Inside, Tiny wires transfer electrical signals around the inside of the device. When you touch a spot, electrical signals shoot all around your device, and cause actions to happen on the screen.