What

interrogative pronoun (3rd person singular inanimate), interrogative determiner / adjective.

Interrogative pronoun

In both English and French, it is considered quite lax to say:

• *You want what?
• Tu veux quoi?

But I am sure that both anglophones and francophones find these phrasings perfectly functional. Nevertheless, normatively it does seem to me that the English proposition is considered "wrong" despite its relative frequence in natural speech. Of course in school we are taught to say:

• What does she want?
   wədə(z/ʊ)
• Qu'est-ce qu'elle veux?
    kesk(ə)

There are two parts to what, the first part -- wh- -- is found in who, how, why, when, etc., the second -- -at -- is found in that