Tracking in StarTools makes sure that every module and algorithm can trace back how a pixel was modified at any point in time. It is the Tracking engine's job to allow modules and algorithms "travel in time" to consult data and even change data (changing the past), and then forward-propagate the changes to the present.
The latter sees the Tracking module re-apply every operation made since that point in time, however with the changed data as a starting point; changing the past for a better future. This is effectively signal processing in three dimensions; X, Y and time (X, Y, t).