Wikipedia definition of immersion is:
the state of consciousness where a “visitor” (Maurice Benayoun) or “immersant” (Char Davies)’s awareness of physical self is transformed by being surrounded in an engrossing environment; often artificial, creating a perception of Presence in a non-physical world.
The article then describes various forms of immersion, being tactical, strategic, narrative, and spatial and provides an example for each. A solid understanding of any concept and research into a theory can only be done well if started owning an understanding of the basis of the research. To attempt to explain the ties between immersion and de-sensitivity to society, you must understand both immersion and de-sensitivity. The article also provides pictures and examples of current forms of virtual reality which can vary from HMD (head mounted displays) to things like “the Cave”