A water softener is a filtration system that removes hardness-causing calcium and magnesium minerals from your water through a process called ion exchange. A water softener addresses one of the most prevalent and devastating water problems: hard water. Hard water wreaks havoc on the modern home. A water softener meant to remove magnesium and calcium in the water. Some water has high amounts of magnesium and calcium minerals absorbed from the earth, making it hard. If the water lacks such minerals or has them in limited quantities, it is regarded as soft. 

 However, underground water in regions with high amounts of chalk, gypsum, and limestone, tend to be hard. Therefore, to make the water soft, a water softener is used to remove the mineral components that make it hard. Water softening is thus the process of removing the calcium and magnesium, among other metal cations in the water.