Creating a Distant Light
A distant light is a infinitely far light source. It is generally used to replicate the light effect from the sun.
A distant light in the GafferThree node parameters and in the Viewer.
Controlling a Distant Light
The object tab serves to specify the Angular Diameter of the distant light (as is explained in more details below) and wether it is Visible to Camera (represented as a disk in the image background). It also presents the Distant Light's transform. While positioning and scaling an infinitely far object makes little sense, adjusting the translation and scale can be useful when manipulating a distant light in the viewport, but only the rotation has an effect when rendering,
The Object tab of a distant light.
The Material tab of a distant light.