The idea is that if a page is relevant to some category, you add a link to the appropriate Category page at the bottom. The category pages should, of course, have CategoryCategory at the bottom so you can search for them from here.
Thus, if you wanted to see everything to do with Games on the wiki, you'd click CategoryGames, and then click the title of that page.
Here are some examples of categories on the ToothyWiki. OK, so it's a list of all the pages that claim to be a category, categorised... :)