MariaDB
From MoodleDocs
MariaDB is a MySQL fork that is developed and maintained by original MySQL developers organised under . It is considered to be more open and is being distributed as default MySQL compatible database by majority of modern linux distributions.
MariaDB is a drop-in replacement, you can use it with any stable supported Moodle version using standard mysqli drivers.
MariaDB driver
Since Moodle 2.6 there is a dedicated driver for MariaDB. It is recommended to explicitly specify mariadb Moodle driver in config.php:
$CFG->dbtype = 'masriadb';
$CFG->dblibrary = 'native';
See MySQL for more information, the setup procedure is nearly identical.