A push-button is a switch in the shape of a small button or knob. When it is pushed it completes an electrical circuit that controls something.[1] For example, a doorbell rings when a person pushes a button, or numbers are displayed on a calculator or even when you are playing a machine game at an arcade.
References
↑"Push button". Academic Press Dictionary of Science and Technology. 1992. Retrieved 15 June 2011.