What is Mixed Reality?

The term “mixed reality” was coined in the early nineties. By definition, it includes everything that stands between total reality and total virtuality. So as soon as we place something digital in our visual perception for interacting with the real world, we are in the reality-virtuality continuum. A Pokémon hiding under your living room table on the mobile phone display is an example of mixed reality (here in the field of augmented reality).
The Mixed Reality Continuum

Augmented Virtuality is only mentioned here for completeness: It turns around the Pokémon example and your real living room table is in an otherwise completely virtual world. But that is more of an academic nature.

Microsoft has adopted the term “Mixed Reality” and has added the actually not included complete virtuality: Microsoft Mixed Reality also covers Virtual Reality. In addition to the Microsoft HoloLens, all new mixed reality headsets are pure virtual reality headsets.
VR solutions based on mobile phones are not part of the mixed reality continuum because they lack an essential component: interaction with the environment. Mixed Reality headsets, by definition, require space tracking for the necessary interaction with real space.

Windows Mixed Reality

Thanks to the availability of Microsoft Windows 10 with the Creators Update in autumn 2017, Windows 10 natively supports a multitude of new mixed reality headsets. Windows Mixed Reality is an integrated software platform for Windows 10 that prepares the operating system for new technologies such as Virtual and Augmented Reality. Microsoft’s vision is a single-interface digital 3D environment that can be accessed with both VR and AR headsets, such as Microsoft’s in-house Hololens.
In addition to the HoloLens, a number of mixed reality headsets are available. A constantly updated overview can be found on the Microsoft Mixed Reality Website.
Details for developers, implementation instructions, and examples can be found in the Microsoft Developer Framework.

Microsoft first described this vision in a promotional video in the summer of 2016 (see the following video).