The Tree of Life is expressed through Sephirots into 4 worlds:
1. Atzilut - archetypal, divine world, world of emanations, level of radiation
It is beyond Keter with three veils of negative existence: nothing, limitless nothing, and limitless light.These veils contain and conceal the unmanifested aspects of the Sephirots. This world is hard to be comprehended by human mind. Keter, as the first perceivable point of manifestation is created by contraction of the limitless light.
2. Beriah - creative world, world of Archangels, level of creation
This world is also far side of human understanding and can be hinted through the expression of the Sephirots in the lower worlds.
3. Yetzirah - formative world, world of Angels, level of shaping
4. Asiyah - manifested world, world of chakras and nadis, physical level
The Tree of Life is the depiction of the descent of the Divine into the manifested world. It contains three Pillars upon which the 10 Sephirots are distributed.
The left side of the Tree - the Pillar of Severity - relates to the left side of the brain which is called Pingala.
The right side of the Tree - the Pillar of Mercy - relates to the right side of the brain which is called Ida.
The Middle Pillar on the Tree of Life is our Spinal Cord - Pillar of Balance or Sushumna.
The upper parts of The Tree of Life are more spiritual.
The 22 Paths on the Tree of Life contain the 22 Letters of the Hebrew aleph-Beth and interconnect the 10 Sephirots, each having its own number.
Sephirot No. 1, Keter is Thought,
Sephirot No. 2, Chokhmah is Wisdom,
Sephirot No. 3, Binah is Understanding,
Sephirot No. 4, Chesed is Mercy,
Sephirot No. 5, Gevurah in Power,
Sephirot No. 6, Tifereth is Glory,
Sephirot No. 7, Netzach is Victory,
Sephirot No. 8, Hod is Identifying with God,
Sephirot No. 9, Yesod is Foundation, and
Sephirot No. 10, Malkuth is Kingdom.
The Sephirot Daat - Knowledge, has no number and is situated in the gap between Chokhmah - Binah, and Chesed - Gevurah.
Each Path connects two Sephirots.
The Paths on the Tree of Life represent our subjective experiences from one state to another. Special emphasis is put on Paths that correspond to so called Mother letters positioned horizontally on the Tree of Life. SHIN connects Chokhmah and Binah, it is a Plane of Fire and corresponds to the Right Pillar - head. This Plane governs the celestial world, which includes the constellation of planets and stars. ALEPH connects Chesed and Gevurah, it is a Plane of Air, and corresponds to the Central Pillar - lungs. The Plane of Air controls the rain. MEM connects Netzach and Hod, it is a Plane of Water, and corresponds to the Left Pillar - abdomen. The Plane of Water is the source of the regular sequence of the seasons. As the Earth revolves around the Sun, the waters of the Earth change appropriately.
To each of the Paths a single Major Arcana (a key or mystery) is connected. The Arcanas represent the Cosmic Elements, and each of the Arcanas is a small Universe for itself. To understand the Arcanas properly, a mental ability of simultaneous differentiation and identification of seemingly inconsistent concepts is needed. This inconsistency exists only in the mind of the observer.
The Sephirot, Emanation or Sphere, is a Symbol of an objective state. The Sephiriot is a number. A number is a primitive form of an Archetype. It is a mediator between people and higher worlds. A number is an alias for a secret law. Symbols are technical help, intuitive ideas, they transform the psychical energy from lesser to greater forms.
We know that the logic of the ego-consciousness does not reach the sub-conscious mind. A symbolic image could be composed of known elements, but behind the whole there can be something hidden, something that cannot be interpreted. That something is of opposite meaning. It is a secret. The unconscious part of our personality understands symbols. By using symbols we can express hardly apprehensible unconscious material.
The symbolic process is unconscious. It is perceived in images, i.e., the messages are received in form of images. Without symbols we cannot get in touch with our unconscious. Therefore, it can be stated that the symbol is a middle way on which the opposites merge to enable new motion.
Kabbalah teaches this path of learning and revealing these symbols.