From page 792-793 of the user guide:
Tracker Pop-Up Menu
With the Tracker tool enabled, right-click over a shape or a selected control point to open the Tracker pop-up menu. Trackers can be created based on a shape’s points, the center point of a shape or the shape’s bounding box. Trackers created in this manner are a concatenation of the shape and layer transformation data. So, why do this? Because, it is a handy way of creating trackers with all of this combined data for use in other programs.
Create Corner Trackers from Shape Bounds
Creates four trackers around the four corners of the shape bounding box.
Create Tracker from Shape Center
Creates one tracker in the center of the shape.
Create Tracker from Points
Creates trackers from selected points.
Create Point Tracker
Planar Tracker track points can be converted to point trackers which can then be treated like any other point tracker; they can be merged, smoothed, averaged, and applied to layers. Right-click on a planar track point, choose Create Point Tracker and a new point tracker is created.