In WordPress, a taxonomy is a way of grouping content together based on common characteristics. WordPress comes with a number of built-in taxonomies, including categories and tags.
Categories are used to group related posts together in a hierarchical manner, with parent and child categories. For example, a website about food might have a parent category called "Recipes" and child categories for different types of cuisine, such as "Italian," "Chinese," and "Mexican."
Tags are similar to categories, but they are not hierarchical and can be used to describe specific details about a post. For example, a recipe for lasagna might be tagged with "noodles," "cheese," and "tomatoes."
In addition to categories and tags, WordPress also supports custom taxonomies, which allows users to create their own taxonomies to organize their content. For example, a website about music might have a custom taxonomy called "Genres" to group posts by the type of music they discuss.
Taxonomy in WordPress is one of those things that everyone use, but they do not know that they are using it. Derived from the biological classification method Linnaean taxonomy, WordPress taxonomies are used as a way to group posts and custom post types together. ... You can register a new custom taxonomy called Topics.