Where it's a zombie apocalypse, a realistic simulation of oral surgery or a book come to life, what matters is if the environment allows you to immerse yourself. Our experiences and the research give us numerous constructs to consider immersion. We'll cover immersion, flow, presence, cognitive absorption, suspension of disbelief, embodiment and more . We'll contrast the authentic with NPIRL or not possible in real life to discuss how much immersion or authenticity is really needed.