get
<form method="get" …
http://www.costam.net/index.php?imie=Stanis%C5%82aw+Lem&plec=M
$_GET['imie'] // 'Stanisław Lem'
$_GET['plec'] //'M'
post
<form method="post" …>
http://www.costam.net/index.php
$_POST['imie'] // 'Stanisław Lem'
$_POST['plec'] //'M'