Here you can find the most important terms - scientifically explained.


Being in essence or effect, but not in fact.

(Sherman and Craig, 2003 following Webster’s New Universal Unabridged Dictionary, 1989; see also Jerald, 2015).

Virtual Environment (VE)

A virtual environment (VE) is general term for a synthetic simulation of an environment that is controlled by a user, such as a video game or 3D factory simulation. Users may for example navigate through or manipulate the environment through input devices.

Virtual Reality (VR)

Virtual Reality (VR) is a special case of a virtual environment, typically characterized by a stereoscopic rendering in which the perspective of the virtual camera is dependent of the user’s perspective, achieved through real-time head tracking. Virtual reality simulations may for example be achieved through head-mounted displays, CAVE systems, or projections, differing in the degree of immersion.

Augmented Reality

Approaches to enhance (augment) the user’s view of a real-world environment with synthetic or simulated information by using displays, tracking, and other technologies (La Viola et al., 2017) that is directly registered to the physical environment (Schmalstieg & Höllerer, 2016). Augmented Reality systems typically 1) combine real and virtual, 2) are interactive in real time, and 3) are registered in 3D (Azuma 1997). Examples are approaches that use optical see-through or video see-through head-mounted displays, or applications that use mobile phone/tablet based augmented reality technology.

Mixed Reality

A set of approaches (including VR and AR) in which real and virtual information are mixed in different combinations (La Viola et al., 2017), typically involving both, virtual world interactions and physical world interactions.


Virtual characters driven by human behavior (Bailenson & Blascovich, 2004).


Virtual characters driven by computer algorithms (Bailenson & Blascovich, 2004).

Virtual Embodiment

“The physical process that employs the VR hardware and software to substitute a person’s body with a virtual one.” (Spanlang, et al., 2014). This process is often associated with perceptual effects such as the ownership of a virtual body, or the perception of agency (control) over a virtual body.

Human-Computer Interaction (HCI)

Human-Computer Interaction (HCI) is a study field that examines the aspects of the interplay between people and interactive technologies. HCI researchers investigate the process of communication between human users and computers/interactive technologies in general (La Viola et al. 2017 following Hix & Hartson, 1993).

3 D User Interface (3DUI)

A user interface that involves 3D interaction, that is, interaction in a real or virtual 3D spatial context (La Viola et al., 2017).


A human reaction to immersion (Slater, 2003). Often referred to as the perception of ‘being there’ when experiencing a virtual environment (Heeter , 1992 following Rheingold, 1991).


The fidelty to which a system tracks actions and delivers displays (in all sensory modalities) in relation to the equivalent real-world sensory modalities describe a systems immersion. Immersion can be objectively assessed (Slater, 2003), for example by assessing the field of view or tracking accuracy of a simulation.

Degrees of Freedom (DOF)

Degrees of freedom depicts the number of independent motions possible, for example of an input device or a virtual object (La Viola et al., 2017).

Artificial Intelligence

The research field of artificial intelligence (AI) “attempts not just to understand but also to build intelligent entities.” (p.1 Russel & Norvig, 2013). AI systems can be described as systems or machines that think humanely, think rationally, act humanly, or act rationally. They do so by utilizing methods such as natural language processing, machine learning, computer vision, robotics, and others (Russel & Norvig, 2013).

Digital Twin

“A digital twin is a digital replica of a living or non-living physical entity. By bridging the physical and the virtual world, data is transmitted seamlessly allowing the virtual entity to exist simultaneously with the physical entity.”

Saddik, A. El (April 2018). “Digital Twins: The Convergence of Multimedia Technologies”. IEEE MultiMedia. 25 (2): 87–92.

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Hix, D., & Hartson, H. R. (1993). Developing user interfaces: Ensuring usability through product and process.

Wiley. LaViola Jr, J. J., Kruijff, E., McMahan, R. P., Bowman, D., & Poupyrev, I. P. (2017). 3D user interfaces: theory and practice.

Addison-Wesley Professional. Sherman, W. R., and Craig, A. B. (2003). Understanding Virtual Reality.

Morgan Kaufmann Publishers. Webster’s New Universal Unabridged Dictionary. (1989). New York: Barnes and Noble Books. Jerald, J. (2015). The VR book: Human-centered design for virtual reality.

Morgan & Claypool. Slater, M. (2003). A note on presence terminology. Presence connect, 3(3), 1-5.

Heeter, C. (1992). Being there: The subjective experience of presence. Presence: Teleoperators & Virtual Environments, 1(2), 262-271.

Rheingold, H. (1991). Virtual Reality. New York: Summit Books. Schmalstieg, D., & Hollerer, T. (2016). Augmented reality: principles and practice.

Addison-Wesley Professional. Azuma, R. T. (1997). A survey of augmented reality. Presence: Teleoperators & Virtual Environments, 6(4), 355-385.

Russel, S., & Norvig, P. (2013). Artificial intelligence: a modern approach.

Pearson Education Limited. Bailenson, J. N., & Blascovich, J. (2004). Avatars. In Encyclopedia of human-computer interaction, Berkshire Publishing Group.