Basically the system is a set of glasses similar to the ones used for Home 3d TV viewing where each eye piece turns on and off at various rates to simulate 3d worlds, however they've also combined two pico projectors above each eye piece along with a tracking sensor in the center bridge. This configuration allows for projecting your viewpoint forward when looking at a reflective fabric, similar to those used in road signs or safety tape, at a scene or world. This allows for everyone around an table to have their own viewpoints and a shared experience for various applications, be it educational or in entertainment such as role playing or board gaming.
In the video above Rick indicated that he specifically created this system with Dungeons and Dragons in mind as their group was fearful of as they got older about if they would be able to get together and play D&D together.
Also one of the cool things is that since there is a lot of the processing done within the glasses themselves they hope to get this so it'll connect to your phone or tablet and can be run straight from that device so no bulky computer to hook up to and play. All you would do is plug into your phone connect to a game/server/whatever and then start playing.
This could revolotionize playing together on a large scale if the end price and production model is both good looking and affordable for either individual or group purchase.
One of the other benefits is that unlike the Occulus Rift you don't get nausea that some people get after using those VR devices. Check out the videos below. The first is Jeri and John over at Tested.com showing off the gear and getting the Kickstarter going. The second is from Jeri's channel and her story of the 18 month journey. The last video is the initial showing at Makerfaire San Mateo last year, (which i totally missed!!).
Here are some other videos demoing/talking about the CastAR system: