Unity Light Probes:
Light Probes are a feature of Unity used to create realistic real-time lighting from baked light sources (E.g. Material light emissions, etc) other than Unity’s various Lights (E.g. Spotlight, Directional Light, Point Light, etc).
Light probes interpret the baked lighting data from the areas of the scene for which they apply, and send that data to dynamic objects so that they can be lit by baked lights.
To use baked lighting, the “light” sources must be static objects, and the lighting type must be baked (not real-time lighting). Baked lighting data can only change when the scene lighting is remapped via the Lighting window in Unity (“Window/Rendering/Lighting”).
Creating a Light Probe Group:
Use the right-click menu, or “GameObject/Light/Light Probe Group” to create a new group.
A “Light Probe Group” GameObject is created in the scene. It contains 8 Light Probes in it. These can be positioned independently.
By placing these probes around your scene in areas you want the baked lighting data to be calculated, you can light up your scene with non-light lights.
In the above images, the guard (the only non-static object) is lit not by an actual light, but by a collection of materials with light emission properties mostly in the computer desk in front of him.