The phase of a UITouch instance changes in a certain order during the course of an event. You access this value through the phase property.
A finger for a given event touched the screen.
A finger for a given event moved on the screen.
A finger is touching the surface but hasn't moved since the previous event.
A finger for a given event was lifted from the screen.
The system canceled tracking for the touch, as when (for example) the user moves the device against his or her face.