Learn French: Qui est chez toi ? - Who is at your place?

Tu is a subject pronoun, used when "you" are doing the action. However, after a preposition like chez (at the home of), French requires a stressed pronoun. The stressed pronoun for the informal "you" is toi.

What exactly does chez mean?

Chez is a very common preposition in French that means "at the home of" or "at the place of." When combined with a stressed pronoun like toi, it translates naturally to "at your house" or "at your place."

Why is the verb est used after qui?

When qui (who) is the subject of a question, it always takes the third-person singular form of the verb, exactly like il or elle (he or she). We do the exact same thing in English when we say "Who is" instead of "Who are".

Could I say chez vous instead of chez toi?

Yes! If you are speaking to someone you address formally, or if you are speaking to a group of people, you would say chez vous. Chez toi is strictly for one person you know well enough to use the informal tu with.