Reverse osmosis is a process in which water is forced through a semipermeable membrane, leaving impurities behind. This process can be used to purify water, making it safe to drink. However, not all bottled waters are reverse osmosis water. In fact, many bottled waters do not undergo any type of filtration or purification process at all. So, if you're looking for reverse osmosis water, be sure to check the label before you buy.