I don't know of any succinct documentation of the license types. The closest thing I've seen are the license descriptions for the various packages when you go to download them. That was on the Cognos site, and I don't know if that is still present on the IBM site.
My salesman seemed to have a semi-difficult time of getting those definitions, so I presume that they are not easily located. If someone knows where this info is hidden - out with it!!!
Our sales person gave us a chart that listed our licenses and which "functionality" (mostly studios) that worked with each and it was AWESOME but that was in Jun 2007 and most if not all of the licenses have since changed. Additionally it seemed this chart was her personal copy and not something from corporate so I don't know that everyone's really "on the same page." It's a mystery. An unnecessarily complicated mystery. If I get a minute this afternoon I'll re-create it and post it with the huge caveat that it's not likely still applicable. (It's just a great format to use to at least create your own comparisons.)