config.php question

[In$ane]

// ****** SLAVE DATABASE CONFIGURATION ******
// If you have multiple database backends, this is the information for your slave
// server. If you are not 100% sure you need to fill in this information,
// do not change any of the values here.
$config['SlaveServer']['servername'] = '';
$config['SlaveServer']['port'] = 3306;
$config['SlaveServer']['username'] = '';
$config['SlaveServer']['password'] = '';
$config['SlaveServer']['usepconnect'] = 0;

ok what is this for i see it in the config is it for a backup like a second data base or will it make vbulletin work faster because i have a second mysql thats the reason i am asking and can you set it up if you been running a forum for a bit...