The function of reverse osmosis (RO) system is to remove impurities and contaminants from water. This is achieved by applying high pressure to water, forcing it through a semi-permeable membrane. The membrane acts as a filter, retaining the contaminants on one side while allowing the purified water to pass through to the other side. This process is called reverse osmosis because it is the reverse of the natural process of osmosis, where water molecules pass through a membrane from a lower concentration to a higher concentration. RO is used in water treatment facilities, households, and industries to purify water for drinking, irrigation, and other uses.