What does a normal ecg with normal variations mean?

Normal: I think you are referring to the general appearance of the ECG complexes along with timed intervals of conduction. This tells us something about the morphology of the heart (ie is it enlarged or is it damaged), as well as the electrical conduction properties ( which might hint at the risks for arrhythmia). These intervals all have a normal range and variability within that range is normal.

Very little : Unfortunately, the conventional ECG is older technology, started mire than 100 years ago. It is only accurate for rhythm disturbances... A new and much better technology based a systems engineering has emerged! it is called multifunction cardiogram! http://en.M.Wikipedia.Org/wiki/multifunction_cardiogram.