Windows hello is a new authentication system coming in Win 10. It helps you log in to windows using facial recognition or fingerprint. Fingerprint based log ins are already part of existing systems, but face recognition is new. Before we go overboard, it does not use the current webcams, but needs new camera hardware which has infrared scanning and 3D imaging support (atleast from what I can get from the articles I have been able to find.
There is also a new technology called "Microsoft Passport", which does not seem to be related to the old passport, but seems to replace password with a hardware based token exchange for authentication to apps or websites.
The following video shows an introduction to some features of Windows Hello.
Also Intel has a video where their new Realsense camera integrated into Hello