Salt Water Reverse Osmosis is a process in which salt and other inorganic solids are removed from sea water to produce fresh water.
RO works by taking the salt water and forcing it through a material known as a membrane that has tiny holes in it. The holes in the membrane allow the fresh water to pass through but stops the salt and other items like sand, grit, weeds, etc.
The fresh water is then chlorinated and put into storage facilities for distribution through the water network.