However, for Jews, gehenna—while certainly a terribly unpleasant place—is not hell. The majority of rabbinic thought maintains that people are not tortured in a hell; but the Hebrew meaning of the world Gehenna is the pit or the grave. It is a spiritual forge where the soul is purified for its eventual ascent to Gan Eden [orignal Garden of Eden], and where all imperfections are purged.
In this sense, it is somewhat similar to the Roman Catholic purgatory. Gehennom (lit: the valley of Hinnom, in Jerusalem; i.e. the gravel) is the sinner's experience in the afterlife. In other words, it's the same "place" as gan eiden (lit: the garden of Eden; i.e. heaven) — it's the perspective of the individual that makes it one or the other.
In some descriptions of the afterlife, we find that beyond Gan Eden there is a little known realm called the otzar, the divine treasury of souls; this is also called the tzror ha-hayyim, the bundle of life. This otzar is a transcendent realm of human souls, in the highest spheres of creation. Before souls are born they are said to come from this treasury, and they return they at some point after death.
Souls are said to originate in a realm called the 'guf' (Avodah Zarah 5a, Nedarim 13b, Yevamot 62a), from which they descend to the earthly reality to animate human bodies. After death, these souls return to the otzar, or tzror ha-hayyim. (Shabbat 152a; Pesikta Rabbati 2:3)
According to the Kabbalah [Jewish mysticism] every human has at least one element in their soul; with the proper study a person can eventually develop two higher levels of the soul. A common way of explaining the three parts of the soul is as follows:
Nefesh - the lower part, or animal part, of the soul. Is linked to instincts and bodily cravings.
Ruach - the middle soul, the spirit. It contains the moral virtues and the ability to distinguish between good and evil.
Neshamah - the higher soul, or super-soul. This separates man from all other lifeforms. It is related to the intellect, and allows man to enjoy and benefit from the afterlife. This part of the soul is provided both to Jew and non-Jew alike at birth. It allows one to have some awareness of the existence and presence of G-d.
The "Raaya Meheimna," a later addition to the Zohar, posits that there are in fact two more parts of the human soul, the chayyah and yehidah. These parts were considered to represent the sublimest levels of intuitive cognition, and were only within the grasp of very few individuals.
Chayyah - The part of the soul that allows one to have an awareness of the divine life force itself.
Yehidad - the highest plane of the soul, in which one can achieve as full a union with G-d as is possible.