Luria's cosmological problem was precise: if Ein Sof, the infinite, fills all conceivable reality without any gap or limit, as its very definition as infinite seems to require, then there is, by definition, no unoccupied space in which a finite, distinct world could come to exist, since anywhere the world might be would already be entirely filled by the infinite divine presence itself; tzimtzum is Luria's proposed solution, a primordial act in which Ein Sof withdraws or contracts its presence from a single conceptual point, leaving behind a chalal, an empty space or void, not truly empty of God in any absolute sense, later Kabbalistic commentary insists, but empty enough, relatively speaking, for a finite creation to be given its own room to exist within it.
Creation, on this account, unfolds within that vacated space through a subsequent process of emanation, a ray of divine light entering the void and gradually differentiating into the ten sefirot, but tzimtzum itself is specifically the prior, enabling contraction that makes any subsequent emanation into a genuinely finite world possible at all, rather than an unbroken infinite flood that would leave no distinct world standing apart from its source. Chaim Vital's Etz Chaim systematized Luria's oral teachings into the school's foundational written form, and it is largely through Vital's transmission that the doctrine reached the wider Kabbalistic tradition beyond Luria's own immediate circle in Safed.