wp_term_relationships 

This used to form the relationship between posts and terms. This table consists of three columns and only IDs are used as data. Let's identify some of the most important columns in this table:

object_id Stores the ID of the post or custom post type that connects with the taxonomy
term_taxonomy_id Stores the ID of the taxonomy

This is purely an associative table, which connects two tables using IDs. As a developer, you just need to assign the relationship, and this table doesn't have different uses based on the type of the site.

Get WordPress Development Quick Start Guide now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.