The document discusses Microsoft HoloLens, an augmented reality headset developed by Microsoft. It begins with an introduction to HoloLens, describing it as an untethered, self-contained computer powered by Windows 10. It then covers the HoloLens hardware including sensors and its custom Holographic Processing Unit. The document explains how HoloLens works by scanning the environment and overlaying holograms. Examples of uses for holograms are provided. SDKs allow developing apps for HoloLens using Visual Studio and Unity. While promising productivity gains, challenges include cost and size.