And when he was alone, they that were about him with the twelve asked of him the parable. And he said unto them, Unto you it is given to know the mystery of the kingdom of God: but unto them that are without, all these things are done in parables:
And he also taught them other things in private. And they taught those who followed them, things both written and not. And all this is part of the Apostolic tradition, the entirety of Jesus’ revelation: the deposit of faith.
It is not hidden or secret, it is taught freely by the Church.
So why did Christ speak in parables?
He answered and said unto them, Because it is given unto you to know the mysteries of the kingdom of heaven, but to them it is not given. For whosoever hath, to him shall be given, and he shall have more abundance: but whosoever hath not, from him shall be taken away even that he hath. Therefore speak I to them in parables: because they seeing see not; and hearing they hear not, neither do they understand. And in them is fulfilled the prophecy of Esaias, which saith, By hearing ye shall hear, and shall not understand; and seeing ye shall see, and shall not perceive: For this people's heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes and hear with their ears, and should understand with their heart, and should be converted, and I should heal them." -- Matthew 13:-10-15"And the disciples came, and said unto him, Why speakest thou unto them in parables?
Do you think Christ was gnostic? Christ appeared to all men. His teaching was not shrouded in darkness or esotericism like the gnostics.
But all men have not been given ears to hear.
He clearly said He spoke in parables so those given ears to hear would hear and be healed and those without ears to hear would not understand and would not be healed.