What does qu est ce qu mean?

It's normally written as "qu'est-ce que", a contraction for "que est-ce que", and it literally means "what is it that", thought it's used the way we'd say "what is". So, it's not a stand-alone phrase. You'd always be asking "qu'est-ce que [something]". For example, in the Talking Heads song Psycho Killer, the singer repeatedly asks "qu'est-ce que c'est" (pronounced kess kuh say), and he's asking "what is this" (or literally, "what is it that this is")