3D printing refers to processes used to synthesize a three-dimensional object in which successive layers of material are formed under computer control to create an object. In this paper, there is a detailed description on the principles of 3D printing. The objective is to understand various processes of 3D printing. The main focus is on the working of different technologies of 3D printing. When it comes to 3D printing, there are multiple materials to choose from. So the paper also highlights on different materials which are used for 3D printing. It also mentions various application areas of 3D printing significantly. Various pros and cons of 3D printing are also discussed.