A lighthearted way to say "yes". The word "chez" does kind of sound like "yes" if you sound both of them out loud, so many people considered it to be a way to say "yes" half-jokingly.
Kelly: Are you from New York?
Jonathan: Chez.
A jokingly, light-hearted way to say "yes".
Kelly: Do you want to hang after school?
Jonathan: Chez!