Distant lights are useful for lighting objects or a backdrop.
A distant light emits uniform parallel light rays in one direction only. You specify a FROM point and a TO point anywhere in the viewport to define the direction of the light. Spotlights and point lights are each represented by a different light glyph. Distant lights and the sun are not represented by glyphs in the drawing because they do not have a discrete position and affect the entire scene.
The intensity of a distant light does not diminish over distance; it is as bright at each face it strikes as it is at the source. Distant lights are useful for lighting objects or a backdrop uniformly.
Distant Lights are not physically accurate. It is recommended that you do not use them in a photometric workflow.