Since WordPress is a dynamic PHP-based application, it requires a database to store all the important data. WordPress uses MySQL to manage database tables and it supports MySQL version 5.6 or greater and MariaDB version 10.1 or greater.
You can have a look at the below image to better understand the tables present in the database of a standard WordPress installation and how they are connected –
For an even better understanding, you may watch the video below –
Or you can read more about WordPress Database Schema from the Database Description codex page.