Whether to apply ambient occlusion to lightmaps. (Editor only).
Ambient occlusion (AO) is an effect that approximates how much ambient light a given point on a surface receives. When you apply AO to a Scene, areas of concavity - such as creases, holes and adjacent surfaces - appear darker.
When this is is set to true, Unity applies AO to lightmaps. When this is set to false, Unity does not apply AO to lightmaps.
This setting affects lightmaps generated by the Baked Global Illumination system. Note that this property relates only to baked AO, and has no effect on any real-time AO post-processing effects.
When Unity serializes this LightingSettings object as a Lighting Settings Asset, this property corresponds to the Ambient Occlusion property in the Lighting Settings Asset Inspector.
Additional resources: Lighting Settings Asset.