While osmosis is a naturally occurring process where solvent molecules spontaneously enter through a semi-permeable membrane into a higher solute concentrate, reverse osmosis purification requires an external force to occur.

Reverse osmosis desalination is a process that purifies seawater or contaminated and undrinkable water sources by forcing water through a membrane, against osmotic pressure, leaving contaminants behind. The result is water devoid of dissolved salts and harmful content.