Reverse Osmosis is a technology that is used to remove a large majority of contaminants from water by pushing the water under pressure through a membrane.
Reverse Osmosis works by using a high pressure pump to increase the pressure on the feed water side and force the water across the membrane, leaving around 95% to 99% of dissolved salts from feed water.
The desalinated water is called permeate (or product) water and he water that carries the concentrated contaminants that did not pass through the RO membrane is called the reject (or concentrate) water.