VR, AR, MR, XR definitions

This glossary contains definitions of specific VR (virtual reality), AR (augmented reality), and MR (mixed reality) terms and acronyms. To search for a term or a definition, simply use the search function of your browser and type the search term you’re looking for.

360° tracking (3DoF):

It is the minimum capability required to produce an immersive experience. Also called 3DoF, 360° tracking allows the VR, AR, or MR device to know the direction a given user is looking at.

AR (augmented reality):

Augmented reality overlays computer-generated content on top of the real world. This superimposed digital overlay can superficially interact with the environment in real-time. AR is primarily experienced via AR smart glasses, but AR headsets also exist.

Built-in front camera:

VR or MR headsets that feature a front-facing camera allow the user to see the real world without having to take the device off. In the case of AR glasses and headsets, a built-in camera allows users to take photos and/or record videos.

CPU (central processing unit):

CPU stands for central processing unit, one of a computer’s or smartphone’s main components. It is also known as a PC’s processor or microprocessor.

DoF (degrees of freedom):

Degrees of freedom are the number of movement types that the user may experience. In VR, headsets offer either 3DoF (360° tracking) or 6DoF (positional tracking).

Eye tracking:

By tracking the user’s gaze, the XR device renders better sharpness and detail to the specific portion of the display that the user is looking at. It can also be used for specific gaming controls. Few headsets have this feature, as the technology is still complex.

Fish tank VR:

This type of VR experience treats users as simple spectators. They may only observe the content, no interaction with the virtual reality environment is possible.

FOV (field of view):

The wider the field of view, the better. For reference, the human field of view (with eye rotation) reaches a maximum of 220°. Most VR headsets provide around 100 degrees.

Fresnel lenses:

Fresnel lenses and their hybrids are the most common type of lenses for virtual reality as they are thinner and lighter than normal lenses.

GPU (graphics processing unit):

The GPU is a computer chip that enables a PC to render images. It is one of the main components on a computer.

Hand tracking:

Some VR, MR, and AR headsets are able to track the user’s hands and gestures for more natural interactions with the content. This is possible either with advanced controllers or with a special module built into/onto the headset.

HMD (head-mounted display):

The term HMD generally refers to VR headsets, but AR glasses and mixed reality headsets are also technically considered as head-mounted displays.

HUD (heads-up display or head up display):

An HUD is a transparent display that allows users to visualize augmented reality content.


Immersion is the feeling of presence in a virtual environment or the degree to which the human brain can be tricked. The more immersive the headset and/or experience is, the more someone may feel that they are actually there.

Inside-out tracking:

The headset uses one or more front-facing cameras to detect its position, with or without the aid of markers. This type of tracking is generally less powerful and accurate than outside-in tracking.


Lighthouse is a positional tracking system developed by Valve for SteamVR and HTC VIVE headsets. To track the user’s position in 6DoF, this system uses base stations (external sensors), also referred to as lighthouses.

Marker-based augmented reality:

(Also called image recognition). Using a camera and some type of visual markers, such as a QR/2D code, to produce a result only when the marker is sensed by a reader.

Markerless augmented reality:

(Also called location-based, position-based, or GPS). Widely implemented application of augmented reality, uses a GPS, digital compass, velocity meter, or accelerometer which is embedded in the device to provide data based on your location.

MR (mixed reality):

Mixed reality (MR) is a digital overlay that allows virtual, 3D elements to integrate, enrich and interact with the real-world environment. MR is also known as XR (extended reality), immersive media, spatial computing, and hybrid reality.


In MR, occlusion is an effect that allows computer-generated objects to be visibly obscured by objects in the real, physical environment.

Outside-in tracking:

The headset makes use of external sensors and/or cameras to accurately track the headset’s position within a delimited space (room-scaling).

Positional tracking:

Positional tracking is the precise tracking of the VR headset’s position and, therefore, the user’s position.

Projection-based augmented reality:

Works by projecting artificial light onto real-world surfaces. Projection-based augmented reality applications allow for human interaction by sending light onto a real-world surface and then sensing the human interaction (i.e. touch) of that projected light.

Proximity sensor:

A proximity sensor is able to detect the presence of an object. Some headsets have proximity sensors to detect if the user is wearing them or not, in order to automatically pause and resume experiences accordingly.

RAM (random access memory):

RAM is an important computer component that temporarily stores data and allows the PC to quickly access specific information. More RAM allows for more fluidity when multitasking or playing games, especially demanding VR/AR experiences.

Room scale or world scale:

Room scale is a term used when an XR device is able to precisely position itself in 3D within a given room volume, allowing the user to walk freely in 6DoF within that delimited space. World scale is Microsoft’s marketing term for room scale.

SDK (software developer kit):

An SDK, also called devkit, is a set of tools used by developers to create applications for specific software, operating system, gaming console, content platforms, etc.

Sensor fusion:

Multiple sensors consolidate their data to provide an overall result that is more precise, nullifying any respective flaws.

Simulation sickness, VR sickness, or cybersickness:

Some users may experience simulation sickness when using a virtual reality headset. Cybersickness symptoms are similar to motion sickness (nausea, dizziness, etc.) and are primarily linked to low refresh rates or a particular VR game/experience.

Spatial audio:

A marketing term used for the type of immersive surround sound experienced in virtual reality.

Spatial computing:

This term identifies the way users interact with computers in their surroundings. It is not restricted to a single location and can apply to the real or virtual world. Examples include how with advancements in technology, users can now interact via speech, gestures, and wearable computing gadgets.

Standalone VR headset:

A standalone virtual reality headset is an HMD that doesn’t require a PC or a smartphone. Common synonyms include all-in-one VR headsets, wireless VR headsets, and autonomous VR headsets.

Superimposition based augmented reality:

Either partially or fully replaces the original view of an object with a newly augmented view of that same object. Object recognition plays a vital role because an application cannot replace the original view with an augmented one if it cannot determine what the object is.

Tethered VR/AR headset:

A tethered VR/AR headset must be connected by cable to a PC (or gaming console, in the case of the Sony PS VR). Tethered virtual reality headsets are also known as desktop VR headsets or PC VR headsets.

VR (virtual reality):

Virtual reality encompasses all immersive experiences and content via a VR headset or HMD (head-mounted display). The content is 100% digital and computer-generated. The current reality is replaced with a new 3D digital environment in which the user is isolated from the real world.

Windows Mixed Reality (Windows MR):

Windows Mixed Reality is a content platform where users can access VR games and experiences via Windows Mixed Reality headsets. This name may be misleading, as Windows MR headsets are in fact virtual reality devices and not mixed reality.

XR (extended reality):

Extended reality is the umbrella category that covers all the various forms of computer-altered reality, including augmented reality (AR), mixed reality (MR), and virtual reality (VR).