Microsoft really wants the Xbox One to be the only device you need to control everything in your living room, and to ensure that's possible they gave the new Kinect an IR blaster. That means it can control virtually anything that you control with a remote, including your TV and any AV receivers you might be using for external speakers.
The Kinect sends infrared signals bouncing around the room until they reach whatever it is you're trying to communicate. That way it can control the volume on your TV or your speakers, change the channel on the TV or the cable box, and conceivably do more than that.
The Xbox One also features HDMI-in capabilities. That means you can route the cable box through the console, which enable another important feature called Xbox OneGuide.