In WordPress a way to group similar items together is defined as the term of Taxonomy. The basic purpose is that it adds a relational dimension to your website’s content. You use categories and tags to group your posts and categories the posts in the case of WordPress. You are defining the taxonomy of those posts after grouping these posts. So the taxonomy can be hierarchical it can be categories and subcategories.
Default Taxonomies In the WordPress by default, three taxonomies loaded:
1. Category — The number of posts in the similar group.
2. Tag — A label that attached to a post
3. Link category — It means a bucket for grouping similar links together
When creating a post then the categories are hierarchical defined. During creating the post tags also defined but Tags do not use hierarchy. When grouping similar links together using the WordPress link manager then link categories are used. These all three out-of-the-box taxonomies are available for use in a default installation of WordPress. Create each category or tag it is a term of that taxonomy.
For example, a category named Web Design is a term of the category taxonomy. A tag named webagency is a term of the tag taxonomy. When you define your own custom taxonomies in WordPress, then you can understand the taxonomy and terms.
Using a solid taxonomy structure you can understand that how you can classify your content using a solid taxonomy structure will make structure website content in WordPress it much easier from the start.