The Ãœbercart Reference Guides are meant to explain a little bit of the modules' internal workings. Use the various sections to find out a little more about how the code operates. If you can't find what you're looking for between the hook/system documentation and these guides, feel free to bring your question to the forums. If something has been overlooked and you've gone digging through code to find the answer, let us know so we can be sure it gets added to the documentation!
These documents are purely meant for referencing and therefore will not have long explanations. Inside you can find quick descriptions of modules, the database schema, Drupal variables, and some important object references (like the order and product objects).