In the real world, daylight does not just come from direct sunlight; it also comes from skylight that is scattered through the atmosphere. 3ds Max offers great realism and accuracy by calculating not only sunlight, but calculating this scattered light as well.
In 3ds Max, the sky is modeled as a dome of infinite radius placed around the scene. Daylight computes the illumination of a point in the scene with reference to all directions around the point where the sky is visible. The sky brightness is not constant over the sky dome, but rather it changes depending upon the position of the sun.