quick question about default theme

im trying to make my own theme in wordpress and im hacking down on all the unneeded things in the kubrick theme. in the header.php file there is this one thing in the head area “<?php wp_head(); ?>” im just wondering, what does this do??? i’ve searched on the wordpress site and cant seem to find this function listed, i have no idea what it is and things seemt o sometimes work fine and sometimes not work at all when i take it out. any help would be appreciated thanks