That means that there is a file called list.php3 that has a variable named $num and that variable is used to determine the contents of what is displayed (meaning that the file is just a 'container' for all the possible num's).
The link could be coded like
<?
$num=1;
echo "<A HREF="http://www.phpbuilder.com/forum/list.php3?num=$num">CLICKME</A>;
?>
of course, the slashes that are going to appear when I post this are not part of the code, but the slashes that I put in are part of the code... ;-)
