Undertale Wiki:Categories
Categories are an easy way of grouping information and navigation. They are displayed atop articles for easier navigation across different pages.
To categorize an article, you can add [[Category:Category name]] to the bottom of the article, below interlanguage links but above {{Variant}}.
Categories may be automatically added by some templates, such as infoboxes. This is the ideal way of categorizing pages, as it otherwise becomes a non-trivial effort to rename categories.
Category pages display a category description and a list of their contents. While the list of contents may be enough for some people, you should strive to display their contents in a more readable manner (e.g. Category:Characters) if they are very frequently visited, or point to an article that does (e.g. Items). To do so, you can edit the category's description page and add the appropriate description.
All categories must be categorized in other categories, except Category:Undertale Wiki, which is the root category of the wiki. Categories can be categorized under other categories the same way regular articles are categorized.