Membranes are famous for their selectivity and permeability. These properties of membranes made them applicable to most of the industries. Great results are obtained in various processes by using membranes. It is important for the development of any process to know its basics and mechanisms of operation. The latest advancements and developments in the characterization techniques helped to visualize the morphology of the membranes, which further helped in better understanding of membranes structure and function. Based upon these studies various principles and models explaining the principles and mechanisms of membrane transport are developed. Therefore, in this chapter various membrane transport mechanisms are discussed in detail to give a clear picture of membrane transport. This will help to develop membranes with better transport profiles for specific feed components. The highlight of the chapter is that the individual membrane processes are presented by explaining their transport mechanisms, which will make the concepts more clear and easy to understand. This will help to easily assess the requirements of a particular membrane process and use them properly for a particular application. This chapter, also contains the techniques and process representing the maximum utilization of membranes in easy and cost effective manner.