momentary switches operate with two different options. On and Off. For the On function to work, the user has to press and hold the button down in order to keep the switch on. The moment the user lets go of the button, the switch automatically switches to the off position. The on position of the switch allows current and voltage to be transferred through the switch to a circuit. The off position stops all flow of current and voltage through the switch.
The word momentary tells us that the switch is designed to be used momentarily, or at a single point in time as opposed to being switched on and staying on until the user switches the switch off.
Some common examples of momentary switches are your keyboard keys, or telephone number keys, or your TV remote control buttons.
Most momentary switches are single pole single terminal (SPST). The single pole (SP) tells us that the switch only controls one side of the voltage polarity (Commonly the positive voltage side). This means that the positive supply is connected through the switch. the single terminal (ST) tells us that there is only one terminal for the power to flow through, so there is only two options (off or on). SPST switches will have two pins that the wires will connect to. One pin (either pin) connects to the power supply. The other pin connects to the circuit. So when the button is pressed down and held down, the circuit will receive power from the power supply. Obviously, when the button is released, all power moving through the switch is stopped.
Other configurations of switches are common as well, although most momentary contact switches will be Single terminal.