Push button LEDs are a type of component that connects two different points in a circuit. When pressed these switch on an LED.
Push button LEDs have a structure made up of four legs; two on one side and two on the other. The two legs on either side connect internally when the push button is pressed, allowing electricity to flow through the circuit.
A single leg of the push button is connected via a 5v supply and the other one is connected with an LED via a resistor. When in neutral (i.e. not pushed) the push button does not allow the current to flow through it, but when it is pressed it completes the circuit and the LED will start to glow. The current will flow all the while when the push button is pressed. As soon as it is released, the LED will be turned off as the push-button breaks the circuit and stops the supply of electricity.