A category tag is a tag of the bottom of an article to show what type of article you created. A category tag helps people find your article plus aids in the prevention of duplicate articles being written. For example, Conservapedia has an article called Maple syrup. At the bottom of that article there is a tag which states that Maple syrup belongs to the category "Food and drink".
Here is how that "Food and drink" category was created at the bottom of the page:
[[Category:Food and drink]]
By adding the above text to this article, it was added to the category of pages called "Food and drink".
If you wanted to put multiple category tags for an article this is easy to do. Here is an example of having multiple category tags for the entry Ice cream:
[[Category:Food and drink]] [[Category:Dessert]] [[Category:Dairy product]]
Technically, you can add categories anywhere in the article, and it will appear at the bottom. However, it is considered good etiquette to put the category tags at the bottom of the article.
- Do not add catagories to articles based upon idealogical or "silly" grounds.