A resistive touchscreen comprises of several layers, out of which the flexible plastic and glass layers are two important electrically resistive layers.When a finger or stylus tip presses down on the outer surface, both the ITO films meet. It is the measure of the resistance of both the layers at point of contact, which leads to get an accurate measurement of the touch position.
A capacitive touchscreen also consists of two spaced layers of glass, which are coated with conductor such as Indium Tin Oxide (ITO). Human body is an electrical charge conductor. When a finger touches the glass of the capacitive surface, it changes the local electrostatic field.