Transoms are incorporated into a door frame. The window above the transom can be in single or multiple panels or a decorative one. It’s rare for a transom window over commercial doors to be used for ventilation like they are in private homes.
Transom windows can be strictly decorative or used to display an address, or a building, or corporate name with or without an address. They are a nice touch to bring additional light into a corporate lobby, for instance.