Articles category basically refers to categories which allow the articles to be placed in either one or more groups so that these may be further subdivided. So, when any article belongs to a particular category, it has a link to the page which describes this category. Likewise, when any sub-category is found to belong to a parent category, it will also contain special links to that parent category page. Every category page will bear an introduction that may be considered as an article and it will always generate multiple links to other articles and sub-categories belonging to that parent category. There is no strict hierarchy because one article can easily be there in multiple categories and each category can also be there in many parent categories.