Abstract: 3D printing is a form of non-traditional machining. Also known as additive manufacturing, it is a method of creating an object by laying successive layers of material until the whole object is created. Unlike subtractive manufacturing processes which usually result in up to 80-90% of the material being wasted, there is seldom any wastage of material in 3D printing. The concept of 3D printing has been around for a long time and its technology has evolved over the years. Different 3D printers make use of different kind of technologies, printing methods and also different kinds of materials. This paper gives a general introduction to the concept of 3D printing, the different types of printing technologies with their advantages, limitation and compares each of them to different criteria such as surface finish, dimensional accuracy, material used, post processing requirements etc.