Definition: What is a Push-Button?
A push button is a mechanical device that acts as a "contact-closure" within a circuit. What this means, is that it acts like a switch which closes a circuit and connects two wires together (this format is known as a "normally-open" configuration). This is similar to the operation that takes place when you turn a light-switch on, and the light connected to it illuminates. The switch connects the light to the power supply. A push-button completes the same operation as the switch and can be referenced either to ground (GND) or the supply voltage (VCC).
Push-buttons sometimes have a "normally closed" configuration where pressing the button "opens" the circuit, or disconnects the two wires attached to the push-button. The push-buttons supplied in Tech-Box.io kits are all "normally open", but you may come across a "normally closed" push-button in some devices.