A push-button or simply button is a simple switch mechanism to control some aspect of a machine or a process. Buttons are typically made out of hard material, usually plastic or metal. The surface is usually flt or shaped to accommodate the human finger or hand, so as to be easily depressed or pushed. Buttons are most often biased switches, although many UN-biased buttons still require a spring to return to their pushed state. Terms for the pushing of a button. include pressing, depressing, mashing, slapping, hitting and punching.