I suppose you are asking about the interrogative. QUE and QUOI don't refer to a person (as opposed to QUI) You have to use QUOI after a preposition QUE dis-tu? Que vois-tu? Que fais-tu? AVEC QUOI joues-tu? DE QUOI as-tu besoin? A QUOI ressemble-t-i? if you are referring to a person __> you should use QUI QUI es-tu? AVEC QUI joues-tu? (avec mon frère)

Quoi means "what." Que is like "that." For example, J'espére QUE tu n'es pas trop fatigué. (I hope THAT you're not too tired) or Il m'a dit QUE je suis marrant (He told me THAT I'm hilarious) Que always follows a noun otherwise you use qui. Qui is followed by a verb. Il y a une fille qui mange. (There is a girl who is/ that is eating) Je sais qu'elle mange.(I know that she is eating) ( Que when followed by a vowel becomes qu' ) I hope this is helpful and if not I'm sure people out there will help to make it more concrete. That's the basics of it anyway. On a final note, qui when referring to people or living things often translates to "who." and for objects it means "that."