Downlights are often called cans or top hats. A type of direct luminaire, they are usually round and recessed in the ceiling. Their principal use is general illumination in a wide range of residential and commercial applications, especially in lobbies, halls, corridors, stores, and other finished spaces. Downlights can be equipped with incandescent, halogen, low-voltage incandescent, compact
fluorescent, or HID lamps.
Downlights typically consist of two parts: the can above the ceiling, and the trim installed from below the ceiling. The can must be suitable for the application.