ShowCursorTracker is an option for Cell which specifies whether an elliptical spot should appear momentarily to guide the eye if the cursor position jumps.
Line breaking is normally set up so that small changes to expressions in input cells rarely cause large-scale reformatting; the cursor tracker appears whenever reformatting is required that makes the cursor position jump.
The cursor tracker is intended to be sufficiently eye-catching to make the low-level human visual system cause an immediate shift in gaze.