Virtual reality immersion is the perception of being physically present in a non-physical world. It encompasses the sense of presence, which is the point where the human brain believes that is somewhere it is really not, and is accomplished through purely mental and/or physical means. The state of total immersion exists when enough senses are activated to create the perception of being present in a non-physical world
A deep mental state of engagement, with suspension of disbelief that one is in a virtual environment.
Exhibited physical engagement in a virtual environment, with suspension of disbelief that one is in a virtual environment.