what does this mean in plain english?

Hi. I'm fairly new to PHP and programming in general. I'm learning mostly by deconstructing what others have written...but even though I have plenty of PHP books and have searched the Internet high and low, I'm stumped by the exact meaning in the following function of what the question mark's ("?") and colon's (":"), mean and do? BTW, I'm not looking for an explanation of the function; just what the question mark's and colon's mean in plain english, so I'll know how to use them in other places. Thanks! Jeff ------------------------------------------------------ function GetSQLValueString($theValue, $theType) { $theValue = (!get_magic_quotes_gpc()) ? addslashes($theValue) : $theValue; switch ($theType) { case "text": $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL"; break; case "int": $theValue = ($theValue != "") ? intval($theValue) : "NULL"; break; } return $theValue; } ------------------------------------------------------