Imagine you are inspecting a 3D model on the computer screen. How would you like if you have the option to rotate, zoom in, zoom out and all with your fingers on the screen, rather than going for the mouse or keyboard. Or say you are drawing a picture... what about dipping your finger in a color and just rubbing it on the screen to paint that picture of yours? Sounds good? Then be ready to welcome multi-touch screens.
Follow the link for a demo video and more info: