Light can be veiled (Tzimtzum-constrictions in Kabbalah) and reflected ("an ascending light from the creations" in Kabbalah). White light divides into seven colors, yet this plurality unites from one source. Divine light divides into the seven emotional sephirot, but there is no plurality in the Divine essence. The term "Ohr" in Kabbalah is constrasted with Ma'ohr, the "luminary", and Kli, the spiritual "vessel" for the light.
Of course, using light as a metaphor for the metaphysical "beyond" can only go so far. Human beings must use these analogies to spatial and temporal phenomenon to understand a spaceless and timeless eternity because that is all most of us know or have experienced.
Once these images are grasped, Kabbalah stresses the need to attempt to transcend them by understanding their deficiencies. Among the limitations of the central metaphor of "light" are the physical inability of the luminary to keep its radiance, the fulfillment of purpose light gives the luminary, and the categorical differentiation between the light source and its light. God created our world, the universe, the Sephirot and so on to infinity by an act of His will. God was not forced to create the Universe or Mankind, and the emanation of Creation did not complete some aspect of God He was lacking; the Godhead was already the Alpha and the Omega- timeless, spaceless and perfect beyond the ability of mere words to describe.
The distinction between the Divine light (beginning with the "Ohr Ein Sof" , which is the primordial "Infinite Light", and subsequently the emanation of the 10 Sephirot) and the Divine esscence (the Ein Sof) appears only relative to Creation. From God's perspective, Scripture states "For I the Eternal, I have not changed."
From the persepective of God's self knowledge, the emanations remain completely united and characterless to their source. This answers early Rabbinic criticism of dualism in Kabbalah. The term in Kabbalah and Hasidic philosophy fo this nullification is Bittul. In daily spiritual life (Dveikus) it inspires the mystical humility of nullification of the ego.
The Ein Sof (literally: "Without End/Limitless/Infinite) is the Kabbalistic term for the Divine essence. Kabbalah describes 10 Sephirot (The 10 Divine emanations or attributes), that reveal the unknowable Godhead to the creations and channel the creative life-force to all levels of existence. Big "however" here- these 10 attributes of God do not represent the Divine essence (the "Luminary").
This difference triumphed over criticism that the Kabbalists were trying to introduce a plurality of gods into the monotheism of Judaism. Kabbalistic texts use great caution to emphasize this difference, and warn against anthropomorphizing the subtle descriptions of Kabbalah in human terms. To avoid such heresies, the historical transmission of Kabbalah was traditionally restricted to direct teaching in close circles.