The Occult

OCCULTISM has its basis in a religious way of thinking, the roots of which stretch back into antiquity and which may be described as the Western esoteric tradition. Its principal ingredients have been identified as Gnosticism, the Hermetic treatises on alchemy and magic, Neo-Platonism, and the Kabbalah, all originating in the eastern Mediterranean area during the first few centuries AD.

While the word "Occult" actually means "Hidden", it is said that it represents hidden knowledge and magic.  There are countless practices around the world that might be labeled as occult. Discussions of the occult here primarily focus on occultism in the Western world, commonly called the Western Occult Tradition or the Western Esoteric Tradition. Some Eastern beliefs have been incorporated into various Western paths, but the systems overall are still primarily Western and are generally rooted in older, Western beliefs. There is no single, overreaching definition of the Western Occult Tradition. Rather, it is composed of a wide variety of different paths and practices such as Hermeticism, Kabbalah, astrology and numerology. Many occultists follow practices involving aspects of multiple paths, which makes generalizing about the occult extremely difficult. In addition, not all followers of these paths label themselves occultists, and outsiders should be sensitive to such differences in definition.

Sources: Dictionary.com, Wikipedia.com, altreligion.about.com