Pages in this wiki can be accessed via the "normal" navigation links at left, the way you would use navbar links on any other website. Additionally, wiki pages can be put into one or more categories, and then the categories can be navigated. This provides a great deal of flexibility in the organization of the wiki, meaning that an indeterminate number of parallel organizational schemes, for whatever purposes, can be used.
The categories are laid out the way the VW manual is organized. This is an organizational scheme that has already been given a great deal of thought, over a period of decades, by extremely well-qualified people. So why fight it? Besides, if somebody is looking for additional material on a topic, then he/she has probably already consulted the manual. If that person comes here looking for information, and finds the same organizational structure, then he/she will already know exactly where to go. Otherwise, he/she will have to get inside the head of a different organization scheme, and that's distracting and sometimes fruitless.
The categories had to be numbered because wiki categories are automatically sorted alphanumerically, so without the numbers, they wouldn't sort the way they are in the manual. They are numbered by 10's, to leave room for organizational changes in the future in the VW manual without having to change as much here to keep it in sync.
VectorWiki Category Tree
How to Add a Page to a Category
If you are editing a page, and want to put the page into a category, the syntax is like this:
[[Category:My Great Category Name]]
When you submit the page, if the "My Great Category Name" category does not already exist, it will be created. Then you have one more thing to do, to put the new category into the main category tree. At the bottom of the page that you submitted, there will be a gray box that will say "Category: My Great Category Name". Click the "My Great Category Name" link. It will take you to a blank page. Edit that page, and enter...
[[Category:My Great Parent Category]]
If "My Great Parent Category" does not exist, it will be created, and then you should repeat the procedure in the paragraph above.
When you (finally) reference a category that is already in the main category tree, the entire newly defined branch will become part of the main category tree.
In other words, to define categories in a wiki, you start from the leaf, and work your way back to the root.
You can define as many categories as you like, and put pages in one or more of those categories. Just don't do it carelessly.
Once defined, a category cannot be renamed explicitly. To "change" the name of the category, you have to go to every sub-category and article in that category, and change the name of the category there. Then you can go back and delete the page for the old category that no longer has any members. In other words, editing categories works the same way as creating categories — you work your way from the leaves back to the root.
Note that category tags can be placed anywhere in a page. If the categorization really only applies to one specific section in a page, it is appropriate for the category tag to be placed in that section, not at the bottom of the page. That way, if the section gets cut-n-pasted to a different page, the category tag will travel along with it. When the page is submitted, the gray category box will still be generated at the bottom of the page, so don't worry that category tags in the middle of the page will create distracting gray boxes in the middle of the page once it's submitted.
Here is the official reference on how categories work in a wiki: How to put a page in a category