Where allowed, pages should be assigned to a category.
There is a finite list of categories, and these are designed to be fairly broad as we do not want lots of categories with only a handful of pages in them. New categories can be requested – contact the website admins.
If a page spans two or more categories, choose the one that is the most prominent in the page.
And, if your page only belongs to one category or spans multiple – don’t forget to tag it.