Don't be.  To my understanding it was a question VERY similar to this from one of Rook's friends that spurred him in to writing the book he is currently working on, as it's something he couldn't just summarise as quickly as you're after.

I'd suggest checking out Rook's section of the forums.

In my ill-educated and little researched point of view, the gnostics were similar in a way to the pagan mysteries of the time.  A few layers to the religion, the outer being that the Christ (Christos) was physically here on earth.  Inner layers that it happened on some other realm and he wasn't a real figure.  Even further inner, that you become the Christos yourself.  To them Jesus  (Yeshua) wasn't a real person on this planet who lived and breathed and died for our sins.  Yeshua being a popular name there's nothing to say there wasn't a person who attained Christos who was named Yeshua, but he wasn't the one spoken of in the bible.

Paul was a gnostic and often frustrated by the inability of his followers to understand what he was teaching about christianity and their inability to get themselves to a stage where he could teach them about the inner sides of the gnostics.  The outer side sounds very much like the christianity we have today and this sounds like the perfect precurser to it to me. 

Rook and others are probably going to reply to this thread saying I have things completely wrong and to ignore what I said, but that's my own understanding of it. :P 

I'm not going to attempt an academic answer, mostly because I am not much of an expert on the subject. I had some thoughts recently on the topic, so let me rephrase the question: "What does Gnosticism means to me?"

Like an amazing number of people on this forum, I was once upon a time a "Christian". Being the smart and curious type I had to know everything about what my church teaches and how it all fits together.

Being the smart and curious type, of course I am going to start asking questions you are not supposed to ask. Most of the answers I got were basically "Its a mystery, and all answers will be revealed in time".

Well being the smart and curious type, I started looking elsewhere for answers and stumbled upon "Godel Escher Bach, an Eternal Golden Braid" by Douglas Hofstadter, which introduced me to much more interesting mysteries than religion could provide. I went to college studying Mathematics, and on the side (because it is more fun than formal college courses) studied philosophy.

I especially enjoyed reading the pre-Christian Greeks, like Plato and Aristotle, the Stoics, and with studying mathematics you cant avoid Pythagoras.

This is how I lost my religious faith. Christianity has lots of holes, the pre-christian philosophers can fill a ton of those holes up with logical and very easy to understand concepts. (Science fills in the rest) The greeks understood the human condition and the problems of society as well as we do today. Humans today have the same flaws and desires as humans did 2500 years ago.

Now it is obvious that the writers of the New Testament not only had access to the great Greek thinkers, but had actually studied them. So why is Plato and Aristotle so much easier to read and far more meaningful than the New Testament, yet people call the latter the "word of god"?

This paradox bothered me for a while until I learned of the Gnostics. Like most christians I was told that the gnostics were a heretical cult that distorted the real christian faith. Most likely the opposite was true, the Gnostics were the real christian faith.

What did they teach that was so heretical to todays Christianity? They cant be that heretical, they wrote much of the New Testament. The heretical part is they considered it "simplistic", appropriate for the "lower" initiates.

What did the "higher" initiates get to learn? First they are taught the truth about Jesus Christ: a mythical allegory symbolizing the journey through life we all take, the death and resurrection is symbolic of a spiritual awakening toward the realization that we are all God. Gnostic mysticism has very close parallels to Budhist mysticism.

Next they taught Plato, and Aristotle, and the Stoics, and Pythagoras.

They also introduced to the goddess Sophia myth, the female half of God (a myth semi-successfully explained in Dan Brown's The DaVinci Code)

If the Gnostics were still around today, they would be politically liberal. Men and women were treated as equals, they were vegetarians, anti-violent pacifists, and were open about sex and accepting of other cultures.

I am not a Gnostic, mostly because the mystical beliefs of the Gnostics are too detached from modern day understanding.

But I feel I have taken the Gnostic journey. First an initiate of the lower levels (Christian), then moving up to the higher levels (Philosophy), then contemplations on the mystical truth (Science).