The Kinect 2.0, an updated natural user interface sensor, was redesigned and recreated to provide motion-tracking and voice commands for the Xbox One.
Kinect 2.0 features a wide-angle time-of-flight camera and a 1080p camera, in comparison to the VGA resolution of the Xbox 360 version, and processes 2GB of data per second to map its environment. Kinect 2.0 has an improved accuracy over its predecessor; it can track up to 6 people simultaneously, referred to as "skeletons", perform heart rate tracking, track controller gestures, and read QR codes to redeem Xbox Live gift cards. By default, voice recognition is active at all times, so the console can receive voice commands from the user, even when the console is in sleep mode. It is possible to wake the console with a command, although settings are available to change which individual Kinect functions are active.
Source: Wikipedia, "[en.wikipedia.org/wiki/Xbox_One%23Kinect_2.0_sensor Xbox One]", available under the CC-BY-SA License.