The structure of the documentation

[jmarzbani]

I have noticed each page of the documentation can fall into one of the following groups: 

1. Concept: these pages usually have a title which starts with "About" ...
2. Task: these pages usually have a title which starts with "To" ... 
3. References: No particular way of distinguishing them

When I land into the home page of the documentation, I expect to see something like a table of contents kind of thing where I can locate the page I am reading in the overall picture. However, the only tree-like table I can see is the User Guide wich seems to be a bunch of Tasks (as I defined above).

My question is: where I can find, for example, a table of all the Concepts, References etc. I don't want to get lost in a maze of pages that take me from one page into another in a random way...