Virtual Reality (VR)
sometimes referred to as immersive multimedia, is a computer-simulated environment that can simulate the physical presence in the real world or imagined worlds. Virtual reality can recreate sensory experiences, which include virtual taste, sight, smell, sound, touch, etc. - Wikipedia
Field of View (FOV)
The field of view (also field of vision, abbreviated FOV) is the extent of the observable world that is seen at any given moment. In case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation. - Wikipedia
Interpupillary distance (IPD)
Interpupillary distance (IPD) is the distance between the center of the pupils of the two eyes. IPD is critical for the design of binocular viewing systems, where both eye pupils need to be positioned within the exit pupils of the viewing system. These viewing systems include binocular microscopes, night vision devices or goggles (NVGs), and head-mounted displays (HMDs).
A simple button made of conductive foil that works as a finger touch. This button was first introduced in 2015 by Google as the new way to control VR Apps when using a Google Cardboard or VR headset. Contrary to the magnetic button used on the classic Google Cardboard, the conductive button works with iOS devices and Android devices.
Head-mounted Display (HDM)
A head-mounted display or helmet mounted display, both abbreviated HMD, is a display device, worn on the head or as part of a helmet, that has a small display optic in front of one (monocular HMD) or each eye (binocular HMD).
There is also an optical head-mounted display (OHMD), which is a wearable display that has the capability of reflecting projected images as well as allowing the user to see through it. - Wikipedia
Head Tracking is a concept which allows a game to follow the movement of the player's head and change what is displayed on the screen relevant to the player's head movements which creates an illusion of 3D where the objects on the screen appears to pop out. - GiantBomb.com
Positional head-tracking tracks the position of your head in space. This will enabled you to look closer to an object by approaching it, walk, and look around corners. Positional head-tracking is achieved by placing an external device which tracks the position of your headset.
Accelerometer and gyroscope
Accelerometers in mobile phones are used to detect the orientation of the phone. The gyroscope, or gyro for short, adds an additional dimension to the information supplied by the accelerometer by tracking rotation or twist.
An accelerometer measures linear acceleration of movement, while a gyro on the other hand measures the angular rotational velocity. Both sensors measure rate of change; they just measure the rate of change for different things.
In practice, that means that an accelerometer will measure the directional movement of a device but will not be able to resolve its lateral orientation or tilt during that movement accurately unless a gyro is there to fill in that info.
With an accelerometer you can either get a really "noisy" info output that is responsive, or you can get a "clean" output that's sluggish. But when you combine the 3-axis accelerometer with a 3-axis gyro, you get an output that is both clean and responsive in the same time." - GSMarena.com
Asynchonous Time Warp
Asynchronous Timewarp or ATW is when timewarp occurs on another thread in parallel (asynchronously) with rendering. Before every vsync, the ATW thread generates a new timewarped frame from the latest frame completed by the rendering thread. ATW fills in the missed frames and reduces judder.