A light that gets emitted in a specific direction. This light will behave
as though it is infinitely far away and the rays produced from it are all
parallel. The common use case for this is to simulate daylight; the sun is
far enough away that its position can be considered to be infinite, and
all light rays coming from it are parallel.
Light probes are an alternative way of adding light to a 3D scene. Unlike
classical light sources (e.g. directional, point or spot lights), light
probes do not emit light. Instead they store information about light
passing through 3D space. During rendering, the light that hits a 3D
object is approximated by using the data from the light probe.
RectAreaLight emits light uniformly across the face a rectangular plane.
This light type can be used to simulate light sources such as bright
windows or strip lighting.