A capacitive touchscreen panel consists of an insulator such as glass, coated with a transparent conductor such as indium tin oxide (ITO). As the human body is also a conductor, touching the surface of the screen results in a distortion of the body's electrostatic field, measurable as a change in capacitance. The location is then sent to the controller for processing.
Capacitive touchscreens are mainly used with human touch input. A standard stylus cannot be used for capacitive sensing, unless it is tipped with some form of conductive material, such as anti-static conductive foam.