It's not the same kind of thing. "Qu'est ce que" is a question like "Qu'est ce que tu fais ce soir ? " ("What are you doing tonight") or "Qu'est ce que c'est que ça" ("What is that ?"). "Que" can be a lot of thing ;) It can be use for a question "Que veux-tu manger?" ("What do you want to eat?"), or a conjunction "Je pense que la vie est belle" ("I think that life is beautifull"), or a pronoun "La voiture que tu as prise" ("The car that you took").

I think you are asking the difference between "QUE dis-tu?" and "Qu'est-ce que tu dis?" Both have the same meaning. You should simply avoid the "QU4EST_CE QUE" form in written French. have a nice day. Martine