A distant light emits uniform parallel light rays in one direction only.
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 for lighting a backdrop uniformly, but they are not physically accurate.
When the light glyphs are displayed, distant lights are represented as wireframe balls in the Scene View. Each distant light has a From and a To point to define the direction of the light.
1 - Normal display of a distant light glyph.
2 - Glyph is highlighted in the scene (when you move mouse over the glyph).
3, 4 - Clicking on the From or To point activates the gizmo for the distant light. You can use it to adjust the distant light's position and target.