In most cases, brands would provide a built-in water softener on their dishwashers to provide better and complete cleaning results. Water softeners are also called ion exchange units or dishwasher salt, where appliances such as dishwashers remove calcium, magnesium, and other minerals to create a soft water.  The soft water is the key essential if you want your dishes to come out spotlessly clean. If you won’t use dishwasher salt or if your dishwasher doesn't have a built-in water softener,  the water might contain a high concentration of calcium and magnesium and this is what is referred to as hard water.