Similar to how having posts and pages as content options can be limiting, sometimes categories and tags just aren't enough. The example of a movie review custom post type might need a variety of new taxonomies or grouping options. Organizing movie reviews by director, movie star, review rating, film genre, and MPAA rating allows visitors to the site to view different groupings of reviews that might interest them. Like the custom post type example, this example creates a very simple taxonomy to test custom taxonomy-specific templates. For this example, a new post taxonomy called Sample Taxonomy is created.
To register this new taxonomy, you use the register_taxonomy function. Adding the following code to the bottom of your theme's functions.php file registers the new sample taxonomy custom taxonomy specifically for WordPress built-in posts, adds a new PostsSample Taxonomy admin menu entry to manage the Sample Taxonomy entries, and adds sample taxonomy options to the editor for posts.
register_taxonomy( 'sample-taxonomy', 'post', array( 'label' => 'Sample Taxonomy' ) );
This function call gives the new custom taxonomy an internal name of sample-taxonomy, assigns the new taxonomy to Posts, and gives the taxonomy a human-readable name of Sample Taxonomy.
After adding this code to your theme, you can create and assign Sample Taxonomies when creating ...