Reverse Osmosis (RO) is the finest of all membrane filtration system, it is a membrane based technology to purify water by separating the dissolved solids from feed stream resulting in permeate and reject stream for a wide range of applications in domestic as well as industrial applications. The objective of this paper is to review the concept of reverse osmosis and the current developments in the RO membrane materials which are the key determinants in the process. This review paper also presents the concept of membrane cleaning, emergence of nanomembranes and mixed matrix membrane materials as well as the various applications of RO systems.