chez
at someone's home
at the premises of a professional, shop or business that represents a person (e.g. "chez le coiffeur")
Je vais chez Julie ce soir.
I'm going to Julie's tonight.
among; within a group
in the case of; characteristic of (someone or something)
Chez les adolescents, ce phénomène est fréquent.
Among teenagers, this phenomenon is common.
Notes
GENERAL INFO
Chez is a preposition. It means "at the home/place of" or "among/in the mind of."
USAGE
It's always followed by a stressed pronoun (e.g., *chez moi*, *chez toi*) or a noun referring to a person or profession (e.g., *chez le médecin*, *chez Jean*, *chez le coiffeur*). It indicates location at someone's residence or workplace.
TRAPS
Do not use chez for inanimate objects; it's exclusively for people, animals, or sometimes businesses representing people. It cannot be followed by an object pronoun (e.g., *chez le* is incorrect for an object).
