1. Qui, Quoi, Qu’est-ce que, Qu’est-ce qui, Ce qui, Ce que

2. QUI = who/whom? QUI means WHO? Can be anywhere in the sentence
Example:
Tu joues avec QUI?
= WHOM are you playing with?
Avec QUI joues-tu?
= with WHOM are you playing?

3. Qu’est-ce que/qu’ = what?
Qu’est-ce que / qu’ means WHAT?
ONLY at the beginning of a sentence
It is the OBJECT of the verb (therefore there will be a new subject following it)
Example:
Qu’est-ce que tu fais? = WHAT are you doing?
object subject

4. Qu’est-ce qui = what? Qu’est-ce qui means WHAT?
ONLY at the beginning of a sentence
It is the SUBJECT of the verb (therefore there will be NO new subject following it)
Example:
Qu’est-ce qui se passe? = WHAT is happening?
subject no new subject

5. = you’re playing with WHAT?
QUOI = what?
QUOI means WHAT?
ONLY at the END of a sentence
Often used with prepositions
It is somewhat ratchet
Example:
Tu manges QUOI?
= you’re eating WHAT?
Vous jouez avec QUOI?
= you’re playing with WHAT?

6. CE QUI = what CE QUI means WHAT
It is the SUBJECT of the verb (therefore there will be NO new subject following it)
Example:
Je comprends CE QUI se passe = I understand what’s happening
subject no new subject

7. CE QUE/QU’ = what CE QUE/QU’ means WHAT
It is the OBJECT of the verb (therefore there WILL be a NEW SUBJECT following it)
Example:
Je comprends CE QUE tu fais = I understand what you’re doing
object new subject