Apologies for the delay in responding. I was giving thought to the best way to answer your questions.
1. How does the camera track the body?
This link may be useful to you in explaining that.
2. Is there a set number of joints it tracks?
As mentioned in the link above, RealSense can track 22 joints in the hand. It can also track 78 facial landmark points.
This link provides much deeper explanation of hand and face tracking.
3. What are those joints?
This link provides the details of the hand joints and face landmarks.
4. How far does the individual have to be from the camera?
The SR300 camera has a min-max depth sensing range of 20 cm to 1.5 m. The R200's min-max range is 30 cm to approximately 4 m. If you want to do hand tracking, the SR300 is the best choice of camera.
5. How many bodies can it track at once?
RealSense can follow one pair of hands (left and right hand), You can track up to four faces with marked rectangles for face boundaries, and select a particular face to focus on. Only one of those faces at a time will have detectable tracking landmarks though.
I think I found a link that is more along the lines of what I am looking for:
is there a good demo or more documentation I could look at on full body movement? Also any documentation on the limitations or issues? for instance how does the camera handle when a joint moves behind another joint? How is the body tracking when you turn completely away from the camera?
When a joint is obscured or you turn completely away from the camera, the tracking stalls as the camera loses sight of the tracked joint.
My own project is a good example of full body movement.