Reverse Osmosis is very similar to the process of membrane filtration. However, there are very distinct differences that separate the two as well. In Reverse Osmosis (commonly referred to as RO) relies on a diffusive mechanism, so that the separation efficiency depends on the solute concentration, pressure and water flex rate. Whereas in filtration there is a removal mechanism for straining to rid of particles regardless of the parameters of the pressure or concentration, like in the RO process.
Reverse Osmosis occurs when using pressure to force a solution through a membrane, retaining the solute on one side, while the purified solvent passes through on the other side.