Taxonomies are the method of classifying content and data in WordPress. When you use a taxonomy you’re grouping similar things together. The taxonomy refers to the sum of those groups. As with Post Types, there are a number of default taxonomies, and you can also create your own.

Taxonomies are normally organized by category and tag.

Default Taxonomies

• categories: a hierarchical taxonomy that organizes content in the post Post Type
• tags: a non-hierarchical taxonomy that organizes content in the post Post Type
• post formats: a method for creating formats for your posts. You can learn more about these on the Post Formats page.