Pushbutton Switch

A pushbutton switch, is a very simple electronic device with 4 pins. When left to itself (open), there is no electrical connection between the two sets of pins. When a switch is pressed, it will close its metallic contact on the two sets of pins, thus allowing current to pass between the 2 sets of 2 pins.

Here’s a brief schematic (note, a set of pins means those pins are always connected, you can see the sets in black, and the mechanism to join them electrically when you press the button in red):