Categories and tags are examples of WordPress taxonomies. If you’re not familiar with the word “taxonomy”, don’t worry! Taxonomy is an academic discipline which defines groups of organisms that have shared characteristics and then names that group.

A taxonomy is a method of classification. WordPress comes with two default methods of classification:

  • Categories
  • Tags

Categories and tags are used to make it easier for your users to navigate your website. Used correctly, they can increase your website’s overall usability.

Each post must have one Category, but it’s up to you whether you have Tags or not.

Some good advice is that your Categories are like your site’s table of contents, and your Tags are for your site’s index.

Categories Categories

Categories is a hierarchical taxonomy. This means that you can create a tree structure, with parent categories and child categories.

For example, if you had the Recipes Category, you could have children such as Starter, Main Course, and Dessert.

The category metabox with a recipes parent category and three child categories

Top ↑

Tags Tags

Tags are a non-hierarchical taxonomy. This means that there are no parents and children, but the information is presented as flat. A post in the Dessert Category might have the tags baking, chocolate, cake, and nuts.

a screenshot of the tags metabox with the nuts, chocolate, baking and cakes tag applied

If you’d like to learn more about Categories and Tags, and how they work, you can read all about Taxonomies in the WordPress Codex.

Top ↑

Custom Taxonomies Custom Taxonomies

Some developers will create Custom Taxonomies for use in their Themes or Plugins. These are simply other ways to classify your content. A Product Types taxonomy might be used for an ecommerce website, or a Portfolio Items taxonomy might be used for a web portfolio. You can read more about Custom Taxonomies in the WordPress Codex.