In English you can ask both “which movie do you want to see” or “what movie do you want to see” and they are essentially the same. In French however, whenever a choice among options is being asked you must use the interrogative adjective quel. For this reason quel can be said to translate as both “which” and “what”. So, the appropriate translation for the movie question is Quel film est-ce que tu veux voir?

You will even find that common questions like “what time is it?” use quelle, not que the word “what”:

   Quelle heure est-il?
   Which hour is it?

In a further lesson, you will learn how quel combines with definite articles to form an interrogative pronoun meaning “which one”.