This document discusses the emerging fields of virtual reality (VR) and augmented reality (AR). It notes that VR completely immerses users in virtual worlds, while AR overlays virtual objects on the real world. Major tech companies are investing heavily in VR and AR, with over $2.5 billion invested in related startups. While estimates of the market size of VR and AR vary widely, mobile VR is expected to significantly outpace desktop VR over the next few years. Major challenges include creating complex and realistic content while controlling costs, as well as defining effective ways to leverage immersive technologies for marketing.