The Kabbalah (like much of modern science) believes life to have come from a tiny point within the centre of nothingness and this is represented by the Sephirot at the top of the tree. This is referred to as Ain Soph Aur (Translated means: Nothing, Limitless, Light). Other Sephiroth are Chokmah where the primordial masculine energy comes in, and Binah where the feminine energy meets the male energy. This is seen to be the start of time itself. In this way the Tree of Life links with so many other systems of where male and female energies form the basis of all creation. Other Sephiroths are the Supernal, which is the plane of divine energy and Malkuth that which relates more to the physical universe. I could go on to describe all the spheres and paths that connect them but really this description is simply an introduction.
To wear this symbol or to have it in your environment is to subscribe to the very essence of the descent of the divine into the manifest world and to feel part of something that has meaning and order.