This page gives an overview of all the categories used in this wiki and of their respective relations. If you're adding pages or images to the wiki, you often need to assign them a category, and it would be really nice if you take this overview into account :) There's also a page that simply lists all the categories used in this wiki: list of all categories. And if you want to check how a specific category is used, you can use the category tree. When you enter a category in the search field on that page, you'll see all its parents and all its children.