Hi,
Basically,
if you have a link like .blabla.php?something=something&somethingelse=somethingelse
PhP will automatically assume you have two vares with values:
$something=something
$somethingelse=somethingelse
Depending ons omse settings (register_globals) these variables will be directly available in the page you just opened (blabla.php) or you can use them by grabbing them from the url:
$something = $GET['something'];
or
$something = $POST['something'];
If you want the full url to play with: this is available through: $_SERVER[REQUEST_URI]