In this era of science we are using many gifts of science in every aspects of our life but without understanding the basic thing "How they are working". A very common thing of today's world is touchpad that every laptop has for its proper use. But do we ever thing how this thing actually works? How our finger movement is understood and then used for different operations. It is basically the magic of electronics.
There are three ways a touch can be sensed
3. Surface acoustic wave
Capacitive sensors are commonly used in laptop touchpads. Two layers of grid sense the change in capacitance at the point of touch and trace the movement of finger. A transducer creates an electric signal based on the movement which is fed into the system to move the cursor and to perform other operations.
Some links for more clear picturehttp://computer.howstuffworks.com/question716.htmhttp://www.ehow.com/how-does_5006535_a-touchpad-work.html