Understanding Virtual Reality, Interface, Application, and Design, by William R. Sherman, and Alan B. Craig, virtual reality experience include -

The Virtuality

An imaginary space that independently exist from the real world. The medium used to create this space is of course a simulation made of visual elements rendered with computer graphics. Relations and interactions between these Element  are defined by rules set by the creator.

Immersion

The users are placed in a virtual space, cut from the real world on a sensory level. VR headsets allow this by occupying their whole field of vision, while headphones achieve the same results with sounds, thus fully immersing the users in another world.

Feedback

Vr headsets track the position of the users within a given space so that the computer renders the changes of positions. Users moving their heads or bodies will be given the illusion that they are moving in the virtual world. The input here is as close to reality as possible, to move around users don’t press a button, they actually move around.

Interactivity

To feel real, a simulated environment should include virtual elements we can interact with: picking up an item, swinging a sword to kill a goblin, breaking a mug, pushing the ignition button of plane in a flight simulator, etc. 

Extended reality (XR) -  real-and-virtual combined environments and human-machine interactions generated by computer technology and wearables, where the 'X' represents a variable for any current or future spatial computing technologies.e.g. It includes representative forms such as augmented reality (AR), mixed reality (MR) and virtual reality (VR) and the areas interpolated among them. The levels of virtuality range from partially sensory inputs to immersive virtuality, VR.

XR is a Super Set which includes the entire spectrum from "the complete real" to "the complete virtual" in the concept of reality–virtuality continuum . Still, its connotation lies in the extension of human experiences especially relating to the senses of existence (represented by VR) and the acquisition of cognition (represented by AR). With the continuous development in human–computer interactions (HCI), this connotation is still evolving.

XR is being applied in a wide range of ways, such as entertainment, marketing, real-estate, training and remote work.

Mixed reality (MR) is the merging of real and virtual worlds to produce new environments and visualizations, where physical and digital objects co-exist and interact in real time. Mixed reality does not exclusively take place in either the physical world or virtual world, but is a hybrid of reality and virtual reality. Augmented reality, a related term, takes place in the physical world, with information or objects added virtually.

There are applications of mixed reality, including design, entertainment, military training, and remote working. There are also different display technologies used to facilitate the interaction between users and mixed reality applications.

 

 

The reality–virtuality continuum encompasses all possible variations and compositions of real and virtual objects. A concept in new media and computer science, but in fact it could be considered a matter of anthropology.