Taxonomy

Categories and tags are built-in taxonomies for posts. Developers can register custom taxonomies for other content-classification requirements. In practical terms, Taxonomy belongs to the publishing and site-management layer. Knowing that layer is important because it tells you what the term can change, what it cannot change, and where to look when something behaves unexpectedly.

The common mistake is to use Taxonomy as if it also meant Category. That blurs two separate decisions and usually sends troubleshooting in the wrong direction. A better test is practical: A taxonomy is the classification system, while each assigned category or tag is a term within that taxonomy.

In day-to-day work, Taxonomy matters when the concept needs to be identified precisely instead of being grouped with a nearby term. The practical value is not the vocabulary itself; it is being able to identify the right control, file, setting or decision when the concept becomes relevant.

WordPress uses taxonomies to group content; categories and tags are the familiar built-in examples for posts. That example is useful because it turns the definition into something you can recognize, test and discuss with other people working on the same project.

Use these references when you need documentation-level detail, specifications or product-specific behavior beyond the plain-English explanation above.