The ever growing demand for fresh drinking water has resulted in a shift in focus towards desalination processes for meeting this growing demand. This chapter gives a detailed look into the need and history of membrane technologies which is followed by in-depth analysis of widely used transport mechanisms for modelling transport of water and salts across the membrane, such as Solution diffusion mechanism and Pore Flow Model. Following which, the limitations of current membrane technology, which include membrane fouling tendencies due to scaling or formation of a biofilm on the membrane surface, have been discussed. Also, recent advancements in membrane technology which hope to counter the limitations such as state-of-the-art membranes and supports with Aquaporin water channels, Carbon nanotubes and Mixed Matrix membrane structures have also been discussed. A glimpse into a techno-economic analysis of various desalination processes along with the advantages of the use of hybrid technologies such as RO-FO and RO-FO-PRO, have been done in length. In all, this chapter provides the reader a comprehensive look into the theoretical modelling as well as the practical aspects of membrane technology.