An apartment (US English) or flat (British English) is a place to live that is only "part" of a larger building. Usually it is a group of rooms on one floor of a highrise building in a city, where land is too expensive for people to have separate houses. An apartment that people own is called a condominium or "condo". A proper apartment has an owner called a landlord who charges money ("rent money" or "rent") from the people who live there ("tenants").