Distilled water is a specific type of water that has all the different impurities of it removed through distillation. Distillation can be achieved by boiling the water and then condensing the steam into a clean container. This product is most commonly used in chemical and biological laboratories because it is a cheaper alternative to deionized water. If you require water that is exceptionally high in purity, then you are going to have to make sure that you use double distilled water, but that is only required in some cases. Another common application is the use of this water to top off lead acid batteries such as the ones you find in cars and trucks.