The Deployment Bunny has a fantastic post over on his blog. 

Read the original post here.

Once again, at 33000 feet over the Atlantic Ocean on my way back from TechEd NA in Atlanta I started to think about all the different properties in MDT 2010 Update 1 that I use which are not really documented, trust me there are “some”. Some of them is, well, not really so useful, but some of them I really use and so should you. So this post is solely made for the purpose of giving you the same “relaxed” life that I have. Hmm, that did not really came out right I think, anyway, You know what I mean, right…

Now, since I not work on that team, I just happen to know them a bit. This is NOT any kind of official description and/or documentation, hopefully will update he documentation sometime around this, especially when virtualization is getting to be more of the standard.