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VR Glossary

Plain-language explanations of terms used in VR hardware, tracking and software. Standards define some words precisely; headset makers may use product terms differently, so check the linked documentation for model-specific claims. Last checked: October 11, 2026.

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24 terms

Definitions

3DoF (three degrees of freedom)

Tracking of orientation around three rotational axes—looking up/down, left/right and tilting—without tracking the headset’s movement through space. Compare 6DoF, which also tracks position. A tracked pose can contain both position and orientation; what a device supports depends on its tracking system. Khronos OpenXR specification.

6DoF (six degrees of freedom)

Tracking both position along three axes and orientation around three axes. It lets an experience respond when you lean or step as well as turn your head. The estimate is a pose reported relative to a reference space; tracking quality and play-area limits vary by device. Khronos OpenXR specification.

Boundary (sometimes Guardian)

A virtual outline or warning system that helps indicate the edge of a defined play area. Meta calls its implementation Boundary and describes it as virtual walls that appear as you approach the area’s edge. Names and behavior differ across platforms; a boundary does not remove physical hazards. Meta: set up a Quest boundary.

DisplayPort (DP)

A digital display connection standard used to carry video from a computer to a display. The specific version, port and adapter path matter: for example, Sony requires a direct DisplayPort 1.4 connection for PS VR2 on PC and says DisplayPort over USB-C is not compatible with its PC adapter. See USB-C and the Sony PS VR2 PC requirements.

Field of view (FOV)

The angular extent of the view visible to a user or rendered by an application. A headset’s advertised FOV is not a complete measure of clarity or comfort; fit, optics and measurement method matter. OpenXR represents each view’s projection using field-of-view angles. Khronos OpenXR specification.

Frame rate (frames per second, FPS)

How many image frames an application renders in a second. It is distinct from a display’s refresh rate: if the app cannot maintain the target, some systems use motion reprojection or other techniques. Actual performance depends on the application, PC and headset settings. Microsoft’s Mixed Reality quality guidance treats frame rate as an app performance target, not a guaranteed headset property.

Head-mounted display (HMD)

A display device worn on the head, typically showing separate views to each eye and often integrating sensors, audio and input. “VR headset” is the more familiar consumer term; hardware features vary by model.

Inside-out and outside-in tracking

Inside-out systems use sensors on the headset or controllers to observe the environment or other tracked signals. Outside-in systems use external sensors or stations to observe tracked devices. These labels describe broad system layouts, not guaranteed precision; hybrid designs exist. Valve describes fixed base-station lasers tracking sensors on Index hardware as one outside-in-style arrangement. Valve Index base stations.

IPD (interpupillary distance)

The distance between the centers of the pupils. Headset lens spacing is adjusted to align the optical sweet spots with the user’s eyes as closely as possible; IPD adjustment mechanisms and supported ranges differ by headset. Meta’s guidance explains its own Quest lens-spacing settings. Meta: IPD and lens spacing.

Mixed reality (MR)

A broad term for experiences that combine digital content with awareness of or interaction with the physical environment. Product labels and feature sets vary: some devices use cameras for passthrough, while others use optical see-through displays. Khronos treats MR as part of the broader XR family; the term alone does not identify a particular capability.

Motion reprojection

A family of techniques that uses recent rendered images and motion information to estimate or transform views when an application misses the display’s desired cadence. It can make motion appear smoother, but may introduce visual artifacts; exact methods and behavior depend on the runtime. Microsoft documents one Windows Mixed Reality for SteamVR implementation as an example. Microsoft: motion reprojection. Compare frame rate and refresh rate.

OpenXR

A royalty-free, cross-platform API standard from Khronos for XR applications to communicate with an XR runtime. It standardizes an interface; it does not make every headset, controller, feature or game automatically interchangeable. Khronos OpenXR 1.1 specification.

Passthrough

A live view of the physical surroundings shown inside a headset, usually captured by cameras. Meta describes Quest passthrough as letting users see a real-time view of their surroundings; image quality, color and supported mixed-reality interactions vary by model. Meta: using passthrough on Quest.

Pose

A tracked object’s position and orientation relative to a coordinate frame. In OpenXR, a pose contains a position and an orientation; it is interpreted relative to a reference space, not as a universal absolute location. Head and controller tracking report poses over time. Khronos OpenXR specification.

Refresh rate

How often a display updates, measured in hertz (Hz). A 90 Hz display refreshes 90 times per second; this does not by itself guarantee that an application renders 90 new frames per second. Compare frame rate and motion reprojection. Headsets and modes may support different refresh rates; Meta’s display-refresh documentation shows that supported rates and frame budgets vary by device and app.

Reference space

A coordinate frame used to express the location and orientation of a tracked view, controller or other object. OpenXR defines spaces such as VIEW, LOCAL and STAGE; which spaces a runtime supports and how they are calibrated can vary. A pose is meaningful relative to a space. Khronos OpenXR specification.

Resolution

The number of pixels used to represent an image or display, commonly listed as width × height. VR specifications may give panel resolution per eye or combined; these are not directly interchangeable. Pixel count alone does not determine perceived sharpness, which also depends on optics, rendering and fit.

XR runtime

The software layer an XR application communicates with to use a headset and other devices, manage frames and access tracking. OpenXR defines the runtime as the interface target for an application; the runtime can manage composition, peripherals and tracking data. Compatibility still depends on supported features and hardware. Khronos OpenXR specification.

Standalone vs tethered VR

Standalone means the headset can run supported experiences using its own onboard computing hardware. Tethered means it depends on a connected computer or console for some or all of the experience. Some headsets support both modes: Meta documents wired USB Link and wireless Air Link, while PS VR2 can be used with PS5 or, through a separate adapter and required PC connections, a Windows PC. Meta Link/Air Link · Sony PS VR2 PC requirements.

SteamVR Tracking (Lighthouse)

Valve’s tracking system uses external base stations that sweep light across sensors on compatible hardware; the stations do not themselves track every generic VR device. Generations and headset/controller compatibility matter: Valve says Index base stations are for 2.0-capable hardware and separately lists Index Controllers as compatible with 1.0 and 2.0 stations. Check the exact component’s compatibility list. Valve base stations · Valve controllers.

Tracking

The process of estimating where an object is and how it is oriented over time. A VR system may track a headset, controllers, hands or eyes, using different sensors and methods. Tracking reports poses relative to a reference space; supported axes, range and reliability vary by device and environment.

USB-C

A reversible connector shape used by many cables and devices; the connector alone does not specify the cable’s data rate, power capability or video support. Verify those separately for the headset and accessory. For example, Meta specifies a USB-C 3.2 cable rated at least 5 Gbps for wired Link, while Sony says DisplayPort-over-USB-C does not work with the PS VR2 PC adapter. Meta Link requirements · Sony adapter requirements.

Virtual reality (VR)

A computer-generated environment presented so that a user can look around or interact as though situated within it. In head-mounted VR, the headset updates the view in response to tracked head movement; the degree of immersion and interaction varies by system.

XR (extended reality)

An umbrella term that includes virtual reality, augmented reality and mixed reality. Khronos uses XR for the continuum of real-and-virtual combined environments and the associated technologies. “XR” does not specify a particular display or tracking feature. Khronos OpenXR specification.

Sources and terminology notes

Standards and primary documentation consulted include the Khronos OpenXR 1.1 specification, Meta’s IPD guidance, Meta’s boundary guide, Meta’s passthrough guide, Valve’s base-station documentation, Sony’s PS VR2 PC requirements, Microsoft’s frame-rate guidance, Meta’s refresh-rate documentation and Microsoft’s motion-reprojection documentation. The Microsoft reprojection page describes one platform-specific implementation, not a universal behavior.

See the VR Accessory Compatibility Finder for a source-linked check of selected accessory categories. For hardware pages, browse the headset directory.