Augmented Reality (AR) is about overlaying pieces of a virtual world over the real world (in contrast to Virtual Reality (VR) that is about replacing the real world with a virtual one). On mobile devices, this simply means enhancing what you can see through the device’s camera with multimedia content (e.g. you can point your camera at a movie poster and watch its trailer, or you can point it at a star in the sky and learn its name). So, basically AR comes down to the following three fundamental questions: where to display what and how.