99. Why does Drupal need a database? What databases are supported?

Drupal stores its information - the individual pages, the registered users, and so on - in the database. The database forms the back-end for your Drupal site. At this time, Drupal supports MySQL (or an equivalent such as MariaDB), PostgreSQL, and in Drupal 7, SQLite.

18 . How database system of drupal works ?

Drupal stores information in a database; each type of information has its own database table. For instance, the basic information about the nodes of your site are stored in the Node table, and if you use the CCK module to add fields to your nodes, the field information is stored in separate tables. Comments and Users also have their own database tables, and roles, permissions, and other settings are also stored in database tables.