Config database specifications

What's the purpose of the two sets of database specs in the core/config.inc.php file?

$database_type = 'mysql';
$database_server = 'localhost';
$database_user = '.....';
$database_password = '........';
$database_connection_charset = 'utf8';
$dbase = 'power10';
$table_prefix = 'modx_';
$database_dsn = 'mysql:host=localhost;dbname=power10;charset=utf8';

These seem redundant. I think I read that the DSN is used by xPDO. What's using the other vars?