Gnosticism encompasses a very wide range of beliefs and is better viewed as a collection of religions sharing some common themes rather than as one specific religion. There are two basic components to beliefs commonly labeled as Gnostic, although the importance of one over the other can vary immensely. The first is gnosis and the second is dualism.
GnosisGnosis is a Greek word for knowledge, and in Gnosticism (and religion in general) it refers to awareness, experience and knowledge of the presence of God. It also frequently refers to self-awareness, as one realizes and recognizes the divine spark within their mortal shell.
DualismDualism, roughly speaking, posits the existence of two creators. The first is a god of goodness and pure spirituality (often called the Godhead), while the second (often called the demiurge) is the creator of the physical world, which has trapped divine souls in mortal form. In some cases, the demiurge is a god in and of itself, equal and opposite to the Godhead. In other cases, the demiurge is a being of lesser (although still considerable) standing. The demiurge might be a specifically evil being, or it might simply be imperfect, just as its creation is imperfect.
In both cases, Gnostics worship only the Godhead. The demiurge is not worthy of such reverence. Some Gnostics were highly ascetic, rejecting the material word as strongly as possible. This is not the approach of all Gnostics, although all are ultimately spiritually focused on gaining understanding of and unification with the Godhead.
Gnosticism and Judeo-Christianity TodayMuch (but not all) of Gnosticism today is rooted in Judeo-Christian sources. Gnostics man or may not also identify themselves as Christian, depending on the amount of overlap between their own beliefs and Christianity. Gnosticism certainly does not require belief in Jesus Christ, although many Gnostics include him in their theology.
Historical GnosticismGnostic thought had a profound impact on the development of Christianity, which traditionally sees a struggle between an imperfect material world and a perfect spiritual one. However, early Church fathers rejected Gnosticism overall as compatible with Christianity, and they rejected the books containing the most Gnostic ideas when the Bible was assembled.
Various Gnostic groups have emerged within the Christian community throughout history only to be branded heretical by orthodox authorities. The most famous are the Cathars, whom the Albigensian Crusade was called against in 1209. Manichaeism, the faith of St. Augustine before he converted, was also Gnostic, and Augustine's writings underscored the struggle between spiritual and material.