Readers of the Bible's canonical New Testament encounter 4 accounts of the life and teachings of Jesus, a number of letters or epistles written primarily to early churches, and an apocalyptic revelation of Earth's final days. This is not to say those texts were the only ones in existence when early Christian church theologians sought to finalize the official Biblical canon. Other epistles and gospels now known as the apocrypha were ultimately rejected for inclusion, either because they could not be properly authenticated or they contained passages deemed too heretical or controversial.
Among these apocryphal texts are a collection of writings called the Gnostic Gospels. The Gnostic Gospels include accounts supposedly written or dictated to others by such notable figures as Judas Iscariot, Mary Magdalene, Mary the mother of Jesus, the "doubting" apostle Thomas and even surviving siblings of the earthly Jesus himself. Some Gnostic Gospels mention details of Jesus' infancy and childhood not found in the canonical Gospels, while others imply Jesus held secret meetings with chosen disciples to discuss issues of a more mystical nature.
The philosophy of Gnosticism which promoted the creation and preservation of the Gnostic Gospels was far more Greek than Judaic in nature. While Jesus Christ Himself may have been a Jewish rabbi preaching to a largely Jewish audience, the Gnostic Gospels strongly suggest He also embraced other philosophical trains of thought, such as Sufism and Greek mysticism. The Gnostic Gospel ascribed to Thomas, for example, speaks of secret sermons hosted by the "Living Jesus," which some Biblical scholars believe took place between Jesus' resurrection and His final ascension into Heaven.
Other Gnostic Gospels may have been written far too late to be considered first-hand accounts of the life of Jesus, although some may have actually been written at the same time as the Gospel of Mark or the unknown "Q," a mysterious early source for Gospel texts. There are theologians who believe the canonical Gospels may have evolved over time, from the dryly factual Gospel of Mark to the more lyrical and emotionally-charged Gospel of John. The Gnostic Gospels may have been other attempts to convey the life events of Jesus to His followers, or some may have been written as more of a private philosophical exercise by Gnostic writers.
For various reasons, the Gnostic Gospels were not accepted by the Christian Church as part of the official Biblical canon. They are available for viewing as part of the New Testament apocrypha, however. Interest in the Gnostic Gospels is said to have grown exponentially following the release of the controversial book and movie The Da Vinci Code. While the idea of finding secret teachings or hidden codes in forbidden texts may sound intriguing, most of the Gnostic Gospels do not contain especially heretical or controversial passages. Some do seem to ignore basic Christian tenets, such as the crucifixion of Jesus, but few go against the essential grain of the canonical Gospels.
Understanding the significance of the Gnostic Gospels would require far more time and research than an article of this scope could possibly provide. Detailed discussions on the Gnostic Gospels and on the Gnostic movement in general can be found online or in research books available in Christian bookstores or well-stocked public libraries.