Buttons and switches come in all shapes and sizes. They can add various functionalities to a project. You can interrupt an electronic circuit by means of a button or switch. You can do this partially or completely. For example, you have an on-off button switch. You can use this to turn one or more lights on or off. You can also use a button to send a signal to a microcontroller such as an Arduino. For example, you can make your own arcade machine.