This circuit is an application of the NE555 monostable trigger. The circuit is in a passive state during normal operation, where pin 3 of the NE555 is at a low level and the LED does not light up. When the touch is stable, the circuit is triggered and enters a temporary state, with pin 3 at a high level and the LED lit up. After a period of time, the transient ends and the circuit flips to steady state, causing the LED to turn off The LED illumination time is 1.1 * R1 * C3.