[astrodust]

Is there a chart or diagram which breaks down what's what?

[mynameisvlad]

That chart would probably be pretty big. Here's a description of the pre-reorg divisions.

http://www.microsoft.com/about/companyinformation/ourbusines...

And an incredibly brief and vague description of the new Engineering Groups:

http://www.microsoft.com/en-us/news/press/2013/jul13/07-11on...