Category:Content using X template

This category is not shown by default on its member pages.

This category can contain pages in different languages. There should be no corresponding language-based categories.

A category of categories which list pages using a particular template.

This wiki used to have a number of categories like this. By placing a category inclusion into a template, you automatically generate a category populated with pages which use that template. This seems useful, but actually it is often unnecessary, since the "What Links Here" feature can also generate a list of template inclusions. Instead of linking to a category you can link like this: [[Special:WhatLinksHere/Template:X|your custom text]]

Such categories should probably be deleted, and indeed most of them have now been.