Piezo switches also known as touch metal piezo switches are an electric switch. Piezo switches do not have any moving parts, this means the lifetime of the switch can be ensured to be tens of millions of operations, since there is no wear involved.
Finger pressure is applied to the surface of the piezo switch, the pressure that is applied activates the piezo element that then converts the pressure to an electric signal that is within the switch housing. This electricity is then used to change the circuit’s orientation.