The chlorine that you constantly dissolve into your pool water or is created by your salt system seeks out and combines with bacteria and other organics on a molecular level, to neutralize these harmful contaminants.  In the process of killing these harmful contaminants the chlorine becomes inactive, and the chlorine and bacteria that have combined together is called “Combined Chlorine”.  The combined chlorine must be removed from the swimming pool to keep your pool water safe and clean and is removed by “Shocking” the swimming pool.  Super chlorinating or “Shocking” means drastically raising the chlorine level of the swimming pool for a short time, to a high enough level that the combined chlorine is burned up.