Gnosticism is currently the source of great interest to diverse groups of people with very different agendas; for those looking for a spiritual identity outside of mainstream Christianity, Gnosticism provides fertile ground for their search, it gives those interested in the origin of Christianity a glimpse at the spiritual landscape when Christianity was still a clandestine cult and those that find value in the mythic and philosophical nature of the cosmologies engendered by the Gnostics(2) find works of astonishing depth and meaning. The word Gnosticism has become problematic in light of the Nag Hamadi find and recent scholarship concerning the early Christian movement. This is largely due to the fact that, until Nag Hamadi, most information about the various sects that are labeled Gnostic came from the Church fathers who wrote antagonistically to the various groups. In fact the Church father Irenaeus seems to have been the first to use the term, in his case it was meant as a derogatory label. Since Nag Hamadi, it has been increasing clear that the portrayal of the Gnostics (so-called) by the Church fathers did not give an adequate accounting of the various sects whose beliefs and doctrines were more diverse than realized and therefore more difficult to precisely define. Some of the main ideas usually associated the Gnostics are

Key Concepts of Gnosticism

Gnosis:
As mentioned above, the word “Gnostic” has of late become a matter of contention between scholars. Some arguing the word itself has become corrupt due to misappropriation by various people resulting in a multiplicity of meanings which renders the word itself meaningless. It is also true that our understanding has advanced to such a degree since the Nag Hamadi find that a single category covering all such movements labeled Gnostic becomes, again, so overbroad as to be practically meaningless. Nevertheless, there is still some merit in considering the word Gnosis. Gnosis, Greek for knowledge, for the Gnostics
was not an intellectual exercise; it was not a passive understanding of some aspect of spirituality. Rather, knowledge had a redeeming and liberating function that helped the individual break free of bondage to the world. (3)
The methodology of obtaining Gnosis was largely a function of the individual groups theology. It may be said, however, that
to be 'Gnostic' should be understood as being reliant not on knowledge in a general sense, but as being specially receptive to mystical or esoteric experiences of direct participation with the divine. Indeed, in most Gnostic systems the sufficient cause of salvation is this 'knowledge of' ('acquaintance with') the divine...(4)
Gnosis, ultimately, was the achievement of salvation, as the attainment was coterminous with victory over the bondage of the Archons or rulers.

Demiurge:
One of the key ideas of many Gnostic sects is a concept borrowed from Plato’s Timaeus. In that dialog, Socrates explains to Timaeus the reasons the Craftsman or Demiurge created the world:
Let me tell you then why the creator made this world of generation. He was good, and the good can never have any jealousy of anything. And being free from jealousy, he desired that all things should be as like himself as they could be. This is in the truest sense the origin of creation and of the world, as we shall do well in believing on the testimony of wise men: God desired that all things should be good and nothing bad, so far as this was attainable. Wherefore also finding the whole visible sphere not at rest, but moving in an irregular and disorderly fashion, out of disorder he brought order, considering that this was in every way better than the other. Now the deeds of the best could never be or have been other than the fairest; and the creator, reflecting on the things which are by nature visible, found that no unintelligent creature taken as a whole was fairer than the intelligent taken as a whole; and that intelligence could not be present in anything which was devoid of soul. For which reason, when he was framing the universe, he put intelligence in soul, and soul in body, that he might be the creator of a work which was by nature fairest and best. Wherefore, using the language of probability, we may say that the world became a living creature truly endowed with soul and intelligence by the providence of God.
-- Plato, Timaeus
For Plato, the Creator is good and God desired that all things should be good and nothing bad, so far as this was attainable. The creation itself is imbued with intelligence since he desired that all things should be as like himself as they could be. Note that the language here implies the understanding that the universe, while created in the likeness if the Demiurge and filled with intelligence could not attain the same perfection as the Demiurge.
For the Gnostics, however, the universe was created in error (via the fall of the Barbelo or lesser Sophia) and was ruled by
(the) inferior Creator-God, also known as the Demiurge. This is Jehovah, the God of the Hebrew Scriptures (Old Testament) …He is viewed by Gnostics as fundamentally evil, jealous, rigid, lacking in compassion, and prone to genocide. The Demiurge "thinks that he is supreme. His pride and incompetence have resulted in the sorry state of the world as we know it, and in the blind and ignorant condition of most of mankind." (5)
This Creator or ruler
is called 'Ialdabaoth', 'Samael '(6) (Aramaic sæm?a-?el, 'blind god') or 'Saklas' (Syriac sækla, 'the foolish one'), who is sometimes ignorant of the superior God, and sometimes opposed to it; thus in the latter case he is correspondingly malevolent.
The demiurge typically creates a group of co-actors named 'Archons', who preside over the material realm and, in some cases, present obstacles to the soul seeking ascent from it

1. Stephan A. Hoeller, The Gnostic World View: A Brief Summary of Gnosticism at http://www.gnosis.org/gnintro.htm
2. such as, for instance, magicians or Jungians.
3. Religious Tolerance, “Gnosticism”, http://www.religioustolerance.org/gnostic2.htm
4. Wikipedia, “Gnosticism”, http://en.wikipedia.org/wiki/Gnosticism
5. Religious Tolerance, “Gnosticism”, http://www.religioustolerance.org/gnostic2.htm
6. See Choronzon for detailed analysis of the Gnostic Samael.
7. Wikipedia, “Gnosticism”, http://en.wikipedia.org/wiki/Gnosticism