This is a type of switch usually in the form of a push button that is only engaged (active) while it is being depressed, as opposed to a typical “on/off’ switch, which latches in its set position. Momentary switches may be normally open or normally closed. A normally open switch doesn’t make contact until and unless it is held down. A normally closed switch is always making contact until the button is pushed. Most electronic (music) keyboard sustain pedals use momentary switches.
Momentary Push Buttons come is different sizes and will take up varying amounts of space on the breadboard.
It is important to understand that momentary push button are a mechanical switch which means that when you press the switch you may get multiple responses/ activations of the switch. This is known as “bouncing”
WHY does this happen? Because the mechanical nature of the button, metal on metal, it will produce multiple signals as the contacts within the button “bounce” or vibrate against each other. Note the multiple signals (peaks) on the image below.
STOP the bouncing single by “debouncing” which is any kind of hardware device or software that ensures that only a single signal will be acted upon for a single opening or closing of the switch or button.