||Four Finger Double Tap.
||Turns VoiceOver gesture help/practice on. This mode can be used to practice the timing and motion of gestures, or to find out if there is a VoiceOver command that matches a particular gesture. For example, if a gesture is made, and VoiceOver is silent, then the gesture being made is not a valid VoiceOver gesture.
VoiceOver Basics: Lesson 1, Section 8.3