here is a simple example php file to get user groups names & their IDs
see Database Methods guidance
<?php
define('IN_MYBB', 1);
require_once "./global.php";
// GET USERGROUPS
$query = $db->simple_select("usergroups", "*", "");
$sep = "";
while($group = $db->fetch_array($query))
{
// GROUPNAME
$groupname = $group['title'];
// GID
$gid = $group['gid'];
$groups .= "{$sep} [ {$gid} ] → {$groupname}";
// SEPERATOR
$sep = "<br />";
}
// OUTPUT
echo $groups;
see Database Methods guidance