The term Gnosticism is derived from the Greek word for knowledge "Gnosis", in that the believers thought that you needed special knowledge to achieve salvation.

Gnostics in that time believed that God was separate from the earth, since the spirit is good and matter is evil. This separation of matter and spirit is at the heart of the heresy. For God's New Covenant to apply, Jesus needed to be both wholly man and wholly God. For Gnostics, Jesus could not since God would not defile Himself to become flesh. The explanation is the Christ joined with the man, Jesus at his baptism by John the Baptist and left him prior to his crucifixion. The leading authority of this theory at the time was Cerinthus.

Given this separation of flesh and spirit, followers of the Gnostic faith would abuse their bodies, either through embracing an ascetic lifestyle, highlighted by punishing the flesh to purify the spirit, or wholly embracing hedonism as the body is evil and its actions cannot corrupt the spirit.

This teaching is completely counter to the Gospel of Jesus Christ.
Salvation is open to all.
Jesus was made flesh to die in our place.
He was risen from the dead so that we may have the promise of eternal life.

Remember, Jesus became flesh. He loved as we love. He laughed as we laughed. He suffered as we suffer. We can take anything to him and he'll understand. He's been through it. And on that day when he returns, we'll be remade with him and forever be part of his kingdom.

For more info, you can take a look at this link.
http://www.carm.org/gnosticism