The Add Atmosphere Or Effect dialog lets you associate an atmosphere or a rendering effect with the light. The list shows either atmospheres, rendering effects, or both. It shows only atmospheres and effects that can be associated with light objects, or that use light objects as their apparatus.
These radio buttons choose what to show in the list.
These radio buttons choose between new or existing effects.
Adding an existing atmosphere or effect creates a new atmosphere or effect whose settings are initially identical to the previous one.