In order to be able to react when a gesture happens, a microphone-like device, that interprets the touch info, is needed. This is where the Gesture Listener comes in play. It gets notified every time a touch happens and triggers any set number of actions.
Touchy uses the Touch Detector in order to capture any inputs that are touch related and sends the touch info to all the registered Gesture Listeners.
You can use as many Gesture Listeners and you want, as only the Touch Detector is responsible for capturing touch inputs and additional listeners will not impact performance in any way.