I need a conceptual overview of TikiWiki and its parts
I'm not a newbie to CMSs, but to TW. I am trying to understand the architecture behind TW, and can't find a clear description so I understand what are the pieces that make up its functionality (I'm not talking about feature set, but pieces that drive the functionality). For example, when I want to create a menu, there are terms such as 'sections' and URL, and 'permissions' and 'Level'. I cannot find a clear definition of what these are, how they work, what they affect, etc.
In the URL field, why is a php script referenced? And why is the same reference for different menu functions, and why do different menu functions have the same name, and what do the different ???_???_?? entries mean in sections and permissions. Is there a good documentation source that gives the answers to these questions?
I keep looking through the online documentation and do Google searches and find plenty of How Tos, but they don't describe what these different parameters mean and why use one over the other. I figure I just haven't found the right place where this is all described, but I've been looking for 3 day now.
TIA