This chapter explains and illustrates the terminology and the different types of Industrial Augmented Reality (IAR) applications according to their purpose and degree of maturity. Augmented Reality is well on its way to becoming a valuable application tool in industry. Certain stages in research and development are required to get there, namely demonstration systems, prototype systems, and productive systems. We discuss the progress made within these requirements, with illustrating examples, and conclude with some lessons learned while implementing Augmented Reality in an industrial context. The information presented here provides valuable insights into the underlying principles and issues associated with Augmented Reality applications. We hope that this chapter becomes a useful resource for all individuals who research or develop Augmented Reality tools.