Tree of Life to be a diagrammatic representation of the process by which the Universe came into being. On the Tree of Life, the beginning of the Universe is placed at a space above the first Sephirah, named Kether or "crown" in English).
Sephiroth, meaning "enumerations", are the 10 attributes/emanations in Kabbalah, through which God reveals himself and continuously creates both the physical realm and the chain of higher metaphysical realms. They should not be understood as ten different "gods" but as ten different ways the one God reveals his Will through the Emanations.
In a numerological sense, the Tree of Life also has significance. Between the 10 Sephiroth run 22 channels or paths which connect them, a number which can be associated with the 22 letters of the Hebrew alphabet. Together the spiritual forces of the 10 Sephirot and the 22 connecting channels are called the "32 Paths of Wisdom".