A lot of information about Kabbalah.

In Judaism, Kabbalah means literally “what has been handed down”, i.e. Tradition. The idea is that just as there is a written scripture or Divine Revelation, the “Revealed Torah (Law)”, this being the Pentateuch (the so-called first five books of Moses; i.e. the first five books of the Old Testament; to which were later appended commentaries like the Talmud, Mishnah, and so on), so there is also an inner or “hidden” Torah, a “secret” (sod), which gives the inner meaning of the Torah, and describes the nature of God, creation, the origin of the Cosmos, the nature of man, and so on. It is this Hidden Torah, which is supposedly handed down by word of mouth (although since the twelfth century it has been committed to writing) that constitutes the Kabbalah.

Kabbalah then, is the occult or mystical branch of the religion, the inner or esoteric counterpart to the outer or legalistic doctrine, the Torah or “Law”, just as Sufism is the occult and mystical tradition within Islam.