The pointing device in the PowerBook G4 computer is a trackpad. The trackpad is a solid-state device that emulates a mouse by sensing the motions of the user's finger over its surface and translating those motions into ADB commands.
The user makes selections either by pressing the trackpad button (below the trackpad) or by tapping and double tapping on the pad itself. The trackpad responds to one or two taps on the pad itself as one or two clicks of the button. The user can tap and drag on the trackpad in much the same manner as clicking and dragging with the mouse. The tap and double tap functions are optional; the user activates or deactivates them by means of the Trackpad control panel.