Touchscreen
A resistive touchscreen has a layer of conducting polyester plastic. When you press on it, you force the polyester to touch the glass and complete an electric circuit. A chip under the screen identifies the coordinates of the place you touched. These screens can sense only one finger at a time and get confused if you try to press in two places at once. They are often used in industrial equipment because it is strong and responds to any kind of input, such as when wearing gloves.