In everyday life, we understand actual physical reality through our sense perception. In the recent years, technology has added many new elements to the perception of reality around us. In this regard, many terms are in use—virtual reality (VR), augmented reality (AR), mixed reality (MR), and more recently, extended reality (XR). In general, these are computer-assisted environments that attempt to recreate reality for the users using cameras, sensors, display and projection devices. However, there are some subtle different among these terms depending upon their relationship with actual physical reality. This chapter makes sense of these terms, with suitable examples in order to present a clear picture for academics and practitioners. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.