Kinect is Microsoft's motion sensor that works as an add-on for the Xbox 360 and Xbox One gaming consoles. The accessory works by providing a Natural User Interface (NUI) that allows users to interact directly without the need for a secondary device, like a controller.
The first generation of Kinect hardware was announced on June 1, 2009 at E3, and released on November 2010 as an attempt to broaden the Xbox 360's audience, and in early 2012 Microsoft released a version for Windows. Some of the competition the Kinect sensor faces is the Wii Remote Plus for Wii and Wii U, PlayStation Move / PlayStation Eye for PlayStation 3, and PlayStation Camera for PlayStation 4.
Microsoft released the first Kinect SDK mid-June 2011, allowing for developers to fully integrate the functionality into their games. The technology behind the Kinect sensor was developed by a subsidiary of Microsoft, Rare, combined with on range camera technology from the Israeli based PrimeSense.
The first three game demo's shown using the Kinect capabilities were Ricochet, Paint Party and Milo & Kate, and since then there have been tons more released.