The word means: "received tradition."

"Kabbalah is on the edge of Judaism," says Rabbi Joe Rooks Rapport, a senior rabbi at The Temple in Louisville, Ky. Rapport is a descendant of Isaac Luria, an influential Kabbalists who lived in the 1500s.

Kabbalah is not a book, but there is a central text, known as the Zohar. Originally written in Aramaic and Hebrew, it's mostly based on Jewish scripture, including the Torah and Talmud and the Book of Ezekiel.

The Zohar is sprinkled with thoughts and interpretations of scripture, instruction on meditation and much more, all with an underlying, puzzle-like pattern that when mastered, can supposedly impart the secrets of God.

"Jewish mysticism is very text-based," Rapport says. "It's a study of layer upon layer of text."

Literal, metaphoric, symbolic and secret meanings can be gleaned from close Kabbalah study, he says.

The popular belief is that the Zohar was written in Spain in the 13th century, although some Kabbalists believe it was written as long as 2,000 years ago.

The figures supposedly telling the stories in the Zohar lived in the earlier era, but Daniel Frank, director of Judaic studies at the University of Kentucky, maintains that was a literary device.

"In order to get a hearing, it presented itself as something old and authentic," Frank says. A 20th-century scholar, Gershom Scholem, is credited with determining that the texts were written in the 13th century.

Two aspects of Kabbalah that have come under scrutiny are numerology and astrology.

"All that is part of this investigation into the universe. Kabbalists believed the movement of the planets and sky could affect their lives," Rapport says. "They believed they could move the planets. They saw themselves as something larger than themselves."

As for numerology, it's true that all Hebrew letters are assigned numerical values. Alef, the Hebrew A, equals 1, Bet, the Hebrew B, equals 2, and so on.

Kabbalists play with the numerical values of words to draw connections within the text and come closer to the hidden meanings.

Plus, "all Hebrew names have meaning," Rapport says. For instance, Adam is derived from both adama, the Hebrew word for earth, and dam, the Hebrew word for blood. Eve comes from hava, meaning "life."

"Those little hints tell you there's a story below," he says.

Kabbalah also has a lot to do with the concept of light.

"Every deed that you do gathers a spark of light that helps bring us closer to the Messianic age," Rapport says. At its highest level, Kabbalistic learning can be used to heal one's self and, eventually, the world, through mitzvot, or good deeds.

But that kind of power and comprehension isn't supposed to come easily.

Unlike his contemporaries, Rapport isn't particularly irked by the current Kabbalah craze. It's not "dangerous or damaging, just superficial," he says.