the ancient Jewish tradition of mystical interpretation of the Bible, first transmitted orally and using esoteric methods (including ciphers). It reached the height of its influence in the later Middle Ages and remains significant in Hasidism.
According to the traditional understanding, Kabbalah dates from Eden. It came down from a remote past as a revelation to elect Tzadikim (righteous people), and, for the most part, was preserved only by a privileged few. Talmudic Judaism records its view of the proper protocol for teaching this wisdom, as well as many of its concepts, in the Talmud, Tractate Hagigah, 11b-13a, “One should not teach … the Act of Creation in pairs, nor the Act of the Chariot to an individual, unless he is wise and can understand the implications himself etc.”
Contemporary scholarship suggests that various schools of Jewish esotericism arose at different periods of Jewish history, each reflecting not only prior forms of mysticism, but also the intellectual and cultural milieu of that historical period. Answers to questions of transmission, lineage, influence, and innovation vary greatly and cannot be easily summarised. Source: wikipedia