This is a simple touch sensor module. You can use it to replace a traditional push button. Using the TTP223 touch detector IC It measures the capacitance of a metallic pad. It can detect the change in capacitance when a finger is near it. This is the same technology used in the iPhone touch screen.This little sensor can “feel” people and metal touch and feedback a high/low voltage level. Even isolated by some cloth and paper, it still can feel the touch. And the sensitivity well decrease as isolation get thick.