[Admin]

There are 7 super global arrays in PHP, as of 4.1.0:
$_GET - contains all information that passed in the address bar (or a form with get method)... used to be $HTTP_GET_VARS.
$_POST - contains all information that is passed through a posted form (if the form was using the post method)... used to be $HTTP_POST_VARS.
$_COOKIE - contains all cookie information... used to be $HTTP_COOKIE_VARS.
$_REQUEST - simply a merge of all three arrays above... new.
$_FILES - contains information about uploaded files... used to be $HTTP_POST_FILES.
$_ENV - all environment variables... new AFAIK.
$_SERVER - all server variables... used to be $HTTP_SERVER_VARS.

Note that in vB3 these arrays are NOT super globals, or at least you must not assume they are. You'll see why when you actually see the code in init.php.