Touch-screens are typically found on larger displays, in phones with integrated PDA features. Most are designed to work with either your finger or a special stylus. Tapping a specific point on the display will activate the virtual button or feature displayed at that location on the display.
There are two major types: capacitive and resistive.
See: Capacitive Touch
See: Resistive Touch Screen
Some phones with this feature can also recognize handwriting written on the screen using a stylus, as a way to quickly input lengthy or complex information.
See: Finger Touch