A recessed light or downlight (also pot light in Canadian English, sometimes can light (for canister light) in American English) is a light fixture that is installed into a hollow opening in a ceiling. When installed it appears to have light shining from a hole in the ceiling, concentrating the light in a downward direction as a broad floodlight or narrow spotlight.
"Pot light" or "canister light" implies the hole is circular and the lighting fixture is cylindrical, like a pot or canister.
There are three parts to a recessed lighting fixture: housing, trim and bulb. The trim is the visible portion of the light. It is the insert that is seen when looking up into the fixture, and also includes the thin lining around the edge of the light. The housing is the fixture itself that is installed inside the ceiling and contains the lamp holder.
There are many different types of bulbs that can be inserted into recessed lighting fixtures, with the amount of heat generated by the bulb being a unique consideration.