Gesture Recognizer

UIGestureRecognizer is the abstract base class for concrete gesture-recognizer subclasses (or, simply, gesture recognizers). The UIGestureRecognizer class defines a programmatic interface and implements the behavioral underpinnings for gesture recognition. The UIKit framework provides six gesture recognizers for the most common gestures. For other gestures, you can design and implement your own gesture recognizer (see “Creating Custom Gesture Recognizers” for details).

http://developer.apple.com/library/ios/#documentation/EventHandling/Conceptual/EventHandlingiPhoneOS/GestureRecognizers/GestureRecognizers.html