Area light
A light with real surface area and size instead of a point, giving soft shadow edges and realistic reflections.
Models the source as a rectangle, disc or tube rather than an infinitely small point. Because the surface sees different parts of the scene, a penumbra forms around every hard shadow, and glossy surfaces mirror the light's actual shape — a window reads as a window in a lacquered car.
Physically accurate but expensive: they require integrating over the whole surface, something real-time engines long faked with tricks until linearly transformed cosines (LTC, 2016) made rectangular area lights practical. They are standard in offline path tracing and now common in photo-studio-style real-time scenes.