Tzimtzum is a concept in Kabbalah that describes a place of void or withdrawal. In modern Kabbalah, tzimtzum is a "vacated" symbolic workspace for G-d to create the universe. In Medieval Kabbalah, tzimtzum was considered the first creative act for concealment and Divine exile.
In modern Kabbalah philosophy, G-d is everywhere and there is no room for a universe to exist outside of Himself. Therefore, in a symbolic sense, He vacated a space within himself, creating a "void" (Heb: Halal) that would allow Him to create his universe. The creation of this void was brought about when God's Infinite Light (Ohr Ayn Sof) was withdrawn from the workspace in which to create the universe. This original withdrawal of G-d's light has been termed tzimtzum (contraction) where G-d's light contracted within Itself to create this so-called void.
Modern Kabbalists describe the creative process as starting with G-d's desire to create. With the creation of the void, through the Tzimtzum contraction, G-d was able to manifest the universe that He desired. However, in order for the creative process to begin, He would have to shine his light back into the void, but not in the same manner as the prior light. This time, G-d's light had to be differentiated so that it lessened Itself to a point where boundaries could be defined. Therefore, G-d established a series of filters, referred to as sefirot, that enable G-d's light to descend from its origins into the void that is located at the farthest point from G-d's ultimate essence.
- Rabbi Ariel (1996). The Ten Sefirot