The Gospel tell the story of the life and teachings of Jesus of Nazareth.
There are four Gospels in the Christian New Testament Bible, those of Matthew, Mark, Luke and John.
The word Gospel is a translation of the ancient greek word euangelion (pronunciation here) which means Good News.
The four Gospels of the New Testament are called synoptic gospels, because they present a similar point of view. They are canonical in that they conform to Christian orthodoxy. The Gnostic gospels are regarded as heresy by Christianity.
The Gnostic gospels are a collection of texts discovered near the Egyptian town of Nag Hammadi in 1945. The Gospel of Thomas is the earliest of these texts.
A Gnostic is an advocate of Gnosticism.
Gnosticism is a religious doctrine that advocates Gnosis as the way to spiritual salvation.
Gnosis refers to mystical or esoteric knowledge that is acquired through direct contact with the divine.
Thus, the Gnostics advocate a religious doctrine based on mystical knowledge that is obtained through direct contact with God.
More information on Gnosticism can be found at gnosis.org