When I first began to delve within gnostic texts there were so many confusing new terms to learn I thought I'd go nuts. Gnostic literature is entrenched in metaphor and pseudonyms to both distance the reader from the question of "who is the author?" and grab their attention concerning the real meaty substance of their writing. A double edged sword, really.
This rampant use of metaphor, personification, directional paradox, and other literary tools confound most beginners. They think they're reading riddles which are purposely created to drive them insane. Gnostic writing is another language and flavor of communication altogether than what modern readers are accustomed to. Equate it with elaborate poetry; something which takes time and patience in order to unravel. Think it's another language? You're right. Most terms are, coincidentally, in Greek. That is the difficult thing to consign yourself to. There is studying involved in the search for gnosis.
I'd like to put together some simplified definitions and examples of basic concepts in gnosticism. There are variations within different sects and even within time frames between gnostic text authors. Once these main ideas are learned and well thought out, real gnosis begins. So yes, you are reading words based in the Greek language. But only because that is where the written ideas began to take shape on paper.... er.. papyrus. You're reading about a completely different way of thinking. And this demands a different discipline of the mind. So relax... and get ready for your brain to be twisted into a knot. I promise it'll be worth it.
Gnosis: Knowledge. To know. To explore learning. Insight. Intuition. Intuitive reasoning. Enlightenment. Knowledge via contemplation.
Gnostic: Person who pursues gnosis. Because of the radical anti-Nicene views of gnostics this has led to quite a bit of trouble for them through the centuries. Dubbed as heretics by the Vatican and often pursued for trial, even today.
Proto(first)-Gnostics: Valentinus, Philo, Basilides, Simon Magus, Cerinthus. Menander of Antioch, Zostrianos, early Sethian leaders, Ptolemy, Heracleon, Mary Magdalen, John the Evangelist, Jesus Christ, St. Paul, Plato .... and dozens more. Too many to name. Many of them were philosophers you've seen and heard of all your life. They all have connections to one another in some way. A great many of them even wrote to one another. And as you can tell from that eclectic list several of these were martyred for their beliefs.
Later Gnostic Leaders: the prophet Mani, St. Augustine of Hippo(until he turned tail and decided he wanted to be a bishop of the Christian Church instead), and the in-hiding leaders of the Manichean, Sethian, Archontic, Basilidean, Cerdonina, and Valentinian sects. After the third century announcing you were a gnostic was akin to putting a neon Shoot Me sign on your forehead. By the fourth century all gnostic books were banned and gnostic meetings were illegal. In the Roman Empire such religious leanings were met with a death penalty. There are many other sects of gnosticism. This list is by no means complete. For example: William Blake is a known gnostic. However he was a cryptic one. A closet gnostic.
Pleroma: Greek, meaning "the fullness." The totality of divine powers. The Divine Principal. The good god. The one who is incomparable and incomprehensible. The All. The one who made the elements that the universe is made from but not the one who made the universe itself. He did not give it form. He simply exists as The All.
Yahweh/God/Jehovah/demiurge/the arrogant one: the Judeo-Christian God described in the New Testament who said in Exodus, "for I, Yahweh your God, am a jealous God." The child of Sophia and the grandchild of pleroma. The one who formed the universe from the elements pleroma made. Also known as the "half-maker" because he had taken the divine substance and fashioned out of it a world. He is the spiritual being who had become forgetful of his origins, even of the ultimate God. He thinks that he is God and there is no other God before him.
Archons: servants of the demiurge. False rulers. The angels and demons of the Old Testament. The lures and distractions of this material world.
Sophia: Greek for "wisdom." This female personality is a bit tricky to pin down. In some Eastern Orthodox Christian sects she is seen as the Virgin Mary. In some gnostic texts she is also known as Eve, in that she was duped or made a mistake which lead to the flaws and separation of man from God. In others she is described as the female child of the Divine Principal. There are correlations between these variations but some are subtle while others are more blatant. The cross over from the Christian tradition into the Gnostic tradition is that "Eve" was the first female child of a god and so was Sophia. Both gave birth. Sophia's childbirth was virginal whereas Eve's was not. So this calling Sophia "Eve" is more of a half-truth based descriptive, merely letting readers know that Sophia was The First of her kind.
The gnostic Sophia was formed out of the mind of The All. Sophia then makes a decision to do some action(text explanations vary widely) and in the process of attempting this, she creates the demiurge(God/Yahweh). Embarrassed, and fearing reprisals from The All, she hides Him away in a void all by himself. God, thinking he's all alone and the only god in existence creates the earth and heavens as well as human beings to worship Him. That's the extremely short and sweet version.
Aeons: emanations of The All. In the various systems these emanations are differently named, classified, and described, but the emanation theory itself is common to all forms of Gnosticism. They are described as existing in layers(like an onion) between human beings and The All. Complex hierarchies of Aeons are thus produced, sometimes to the number of thirty. These Aeons belong to the purely ideal, noumenal, intelligible, or supersensible world; they are immaterial, they are hypostatic ideas. Together with the source from which they emanate they form the Pleroma ("region of light"). The lowest regions of the Pleroma are closest to the darkness—that is, the physical world.
*******************In the Letter of Peter to Philip, Peter is relating a mystic occurrence on the Mount of Olivet in which the spirit of Jesus appeared to teach them.
On The Deficiency of the Aeons:"To begin with, concerning the deficiency of the aeons, this is the deficiency. When the disobedience and the foolishness of the mother(Sophia) appeared, without the command and majesty of the father, she wanted to set up eternal realms. When she spoke, the arrogant one(demiurge) followed. But when she left behind a portion, the arrogant one grabbed it, and it became a deficiency. This is the deficiency of the aeons.
"When the arrogant one took a portion, he sowed it. He placed powers and authorities over it, and he confined it within the mortal realms. All the powers of the world rejoiced that they had been brought forth. But they do not know the preexistent father, since they are strangers to him. Rather, he was given power, and they served him and praised him.
"But the arrogant one grew proud because of the praise of the powers. He was jealous and wanted to make an image in place of an image and a form in place of a form. He assigned the powers within his authority to mold mortal bodies. And they came into being from a misrepresentation of the appearance."
On Fighting The Rulers, Peter relays:The messengers worshiped again, saying, "Lord, tell us, how shall we fight against the rulers, since the rulers are over us?"
A voice called out to them from the appearance, saying, "You must fight against them like this, for the rulers fight against the inner person. You must fight against them like this: come together and teach salvation in the world with a promise. And arm yourselves with my father's power, and express your prayer, and surely the father will help you, as he helped you by sending me. Do not be afraid. I am with you forever, as I already said to you when I was in the body."
(Deficiency is also synonymous in gnostic texts with "smallness" or "pettiness.")