Help:Categories
You can place an article in a category by adding the string [[Category:Example]] to the article's text (where Example is the name of the category). A list of categories may be found at Special:Categories.
The category feature has several functions:
Sort keys
All articles in a given category are sorted alphabetically. If you want an article to be sorted by something other than its name, you should use the following link form in the article's text: [[Category:Example|Sort key]] (where Example is the category name, and Sort key is the value to sort the list by).
For example, by default, the article Bart Simpson will be listed under the individual's first name, "B", because it is the first letter of the article's name. You could instead force the article to be listed by the individual's last name ("Simpson") by using the string [[Category:Characters|Simpson, Bart]].
Remember that sort keys are case sensitive, with capital letters being sorted before lowercase letters. Therefore, Simpson, Bart would appear in the list before seymour skinner.
Linking to a category
In order to link to a category without the current article being added to that category, place a colon before the word "Category" inside the link.
Example: [[:Category:Main Characters]]
Sub-categories
Category pages may be added to other categories and are then recognized as sub-categories. For example, you could edit [[Category:Main Characters]] and add the link [[Category:Characters]]. The Main Characters category would then be a sub-category of the Characters category.