Kabbalah (alternately Kabbala, Qabalah, Qabala, Cabalah or Cabala) (lit. "receiving") is a discipline and school of thought discussing the mystical aspect of Judaism. It is a set of esoteric teachings meant to define the inner meaning of both the Tanakh (Hebrew Bible) and traditional Rabbinic literature, as well as to explain the significance of Jewish religious observances.

According to the Zohar, generally considered the foremost kabbalistic text, Torah study uses four levels (PaRDeS) of interpretation (exegesis) of its text:

• Peshat (lit. "simple")—the direct meaning.
• Remez (lit. "hint[s]")—the allegoric meaning (through allusion).
• Derash (from Heb. darash: "inquire" or "seek")—midrashic (Rabbinic) or comparative meaning.
• Sod (lit. "secret" or "mystery")—the inner meaning—a foundation of the kabbalah.

Kabbalah is considered, by its followers, as a necessary part of the study of Torah – the study of Torah (the Law of God) being an inherent duty of observant Jews. Kabbalah teaches doctrines that are accepted by some Jews as the true meaning of Judaism while other Jews have rejected these doctrines as heretical and antithetical to Judaism.
The origins of the actual term Kabbalah are unknown and disputed to belong either to Solomon ibn Gabirol (1021 - 1058) or else to the 13th century CE Spanish Kabbalist Bahya ben Asher. While other terms have been used in many religious documents from the 2nd century CE up to the present day, the term Kabbalah has become the main descriptive of Jewish esoteric knowledge and practices. The Kabbalistic literature, which served as the basis for most of the development of Kabbalistic thought, divides between early works such as Heichalot and Sefer Yetzirah (believed to be dated 1st or 2nd Century CE) and later works dated to the 13th century CE, of which the main book is the Zohar representing the main source for the Contemplative Kabbalah ("Kabbalah Iyunit").
According to Kabbalistic tradition, knowledge was transmitted orally by the Patriarchs, prophets, and sages (Hakhamim in Hebrew), eventually to be "interwoven" into Jewish religious writings and culture. According to this tradition, Kabbalah was, in around the 10th century BCE, an open knowledge practiced by over a million people in ancient Israel, although there is little objective historical evidence to support this thesis.
Foreign conquests drove the Jewish spiritual leadership of the time (the Sanhedrin) to hide the knowledge and make it secret, fearing that it might be misused if it fell into the wrong hands. The Sanhedrin leaders were also concerned that the practice of Kabbalah by Jews deported on conquest to other countries (the Diaspora), unsupervised and unguided by the masters, might lead them into wrong practice and forbidden ways. As a result, the Kabbalah became secretive, forbidden and esoteric to Judaism (“Torat Ha’Sod” Hebrew: תורת הסוד ‎) for two and a half millennia.
It is hard to clarify with any degree of certainty the exact concepts within Kabbalah. There are several different schools of thought with very different outlooks; however, all are accepted as correct. Modern Halakhic authorities have tried to narrow the scope and diversity within Kabbalah, by restricting study to certain texts, notably Zohar and the teachings of the Isaac Luria as passed down through Haim Vital. However even this qualification does little to limit the scope of understanding and expression, as included in those works are commentaries on Abulafian writings, Sepher Yetzirah, Albotonian writings, and Brit Menuhah. It is therefore important to bear in mind when discussing things such as the Sephirot and their interactions that one is dealing with highly abstract concepts that at best can only be understood intuitively.