The Tree of Life, or Etz haChayim in Hebrew, is a mystical symbol used in the Kabbalah of esoteric Judaism to describe the path to God and the manner in which He created the world ex nihilo (out of nothing). The Kabbalists developed this concept into a full model of reality, using the tree to depict a map of creation. The tree of life has been called the "cosmology" of the Kabbalah. Some believe the Tree of Life of the Kabbalah corresponds to the Tree of Life mentioned in Genesis 2:9. This mystical concept was later adopted by some esoterically inclined Christians as well as Hermeticists.
The Tree Of Life is a diagram representative of the process by which, Kabbalists believe, the universe came into being. On the Tree of Life the beginning of the universe is placed at a space above the first Sephiroth, or Kether, which means the Crown in English. It is not always pictured in reproductions of the Tree of Life, but is referred to universally as Ain Soph Aur (Ain - Without, Soph - End, Aur - Light). To the Kabbalists, it symbolises that point beyond which our comprehension about the origins of Being cannot go any further; it is considered to be an infinite nothingness out of which the first 'thing' (thought of in science and the Kabbalah to be energy) exploded to create a universe of multiple things. Kabbalists also do not envision time and space as pre-existing and place them at the next three stages on the Tree of Life. First is Kether, or the Crown in English, which is thought of as the product of the contraction of Ain Soph Aur into a singularity of infinite energy or limitless light. In the Kabbalah, it is the primordial energy out of which all things are created. The next stage is Chokmah, or Wisdom, which is considered to be a stage at which the infinitely hot and contracted singularity expanded forth into space and time. It is often thought of as pure dynamic energy of an infinite intensity forever propelled forth at a speed faster than light. It is considered to be the primordial masculine energy, which is also referred to in Chinese Taoist philosophy as Yang. Next comes Binah, or Understanding, which is thought of as the primordial feminine energy, the Supernal Mother of the universe which receives the energy of Chokmah, cooling and nourishing it into the multitudinous forms present throughout the whole cosmos. It is also seen as the beginning of Time itself. It is analogous to the Chinese concept of Yin which together with Yang are considered to be the basis of all of creation. There are many parallels between Taoist philosophy and the Kabbalistic conceptions of the Tree of Life. Numbers are very important to Kabbalists and the Hebrew letters of the alphabet also have a numerical value for the Kabbalists. Each stage of the emanation of the universe on the Tree of Life is numbered meaningfully from one, or the Sephiroth of Kether to ten, or the Sephiroth of Malkuth. The nature of each number is thought to express the nature of its Sephiroth.
The first three Sephiroth, called the Supernal Sephiroth, are considered to be the primordial energies of the universe. The next stages of evolution on the Tree of Life are considered to exist beyond a space on the tree, between the Supernals and the other Sephiroth, called the Abyss, because their levels of being are so distinct from each other that they appear to exist in two totally different realities. The Supernal Sephiroth exist on a plane of divine energy. This is why another correspondence for Binah is the idea of suffering, because the Supernal Maternal energy gives birth to a world that is inherently excluded from that Divine Union. After Binah the universe gets down to the business of building the materials it will need to fulfill its evolution and creating new combinations of those materials until is so dense that by the stage of Malkuth the initial pure limitless energy has 'solidified' into the physical universe. Since its energies are the basis of all creation the Tree of Life can potentially be applied to any area of life, especially the inner world of man, from the subconscious all the way to what Kabbalists call the higher self.
But the Tree of Life does not only speak of the origins of the physical universe out of the unimaginable, but also of man's place in the universe. Since man is invested with Mind, consciousness in the Kabbalah is thought of as the fruit of the physical world, through whom the original infinite energy can experience and express itself as a finite entity. After the energy of creation has condensed into matter it is thought to reverse its course back up the Tree until it is once again united with its true nature. Thus the Kabbalist seeks to know himself and the universe as an expression of God, and to make the journey of Return by stages charted by the Sephiroth, until he has come to the realisation he sought.