The Synoptic Gospels (Matthew, Mark and Luke) are the earliest of the four Gospels and were written from a common point of view. They are in very substantial agreement with one another. Herein, Jesus really walks the Earth, and his body has substance and weight. His voice vibrates to his changing mood. He loves and hates, caresses and curses, pleads and labors, exults and sings and dances. Jesus is not God himself, but a mere prophet among men... with all the flaws that are common among men. He was an ascetic who only accepted other ascetics as followers!
And when he was gone forth into the way, there came one running, and
kneeled to him, and asked him, Good Master, what shall I do that I may
inherit eternal life? And Jesus said unto him, Why callest thou me
good? there is none good but one, that is, God. Thou knowest the
commandments, Do not commit adultery, Do not kill, Do not steal, Do
not bear false witness, Defraud not, Honour thy father and mother. And
he answered and said unto him, Master, all these have I observed from
my youth. Then Jesus beholding him loved him, and said unto him, One
thing thou lackest: go thy way, sell whatsoever thou hast, and give to
the poor, and thou shalt have treasure in heaven: and come, take up
the cross, and follow me.
— Mark 10:17-21
The Jesus of the Synoptics is a lot like the hippies of the 1960s, who revolted against the cultural standards of their parents... or like Gandhi, who revolted against the British empire. While worthy of admiration, he was still a mere man, not "God made flesh". And although overall pacifistic in nature, he was first and foremost a rebel against the authorities of his days, living and promoting a rather ascetic life removed from mainstream society.
If any man come to me, and hate not his father, and mother, and wife,
and children, and brethren, and sisters, yea, and his own life also,
he cannot be my disciple. And whosoever doth not bear his cross, and
come after me, cannot be my disciple. For which of you, intending to
build a tower, sitteth not down first, and counteth the cost, whether
he have sufficient to finish it? Lest haply, after he hath laid the
foundation, and is not able to finish it, all that behold it begin to
mock him, Saying, This man began to build, and was not able to finish.
Or what king, going to make war against another king, sitteth not down
first, and consulteth whether he be able with ten thousand to meet him
that cometh against him with twenty thousand? Or else, while the other
is yet a great way off, he sendeth an ambassage, and desireth
conditions of peace. So likewise, whosoever he be of you that
forsaketh not all that he hath, he cannot be my disciple.
— Luke 14:26-33
The Jesus of John is very different. He is totally lacking the passion, the humanity that is abundantly found in the Jesus of the Synoptics. Instead, the Jesus of John is described as a superhuman embodiment of God itself. Unlike in the Syntopics, the whole atmosphere of the gospel of John is repressed, ethereal, supernal, eerie. And unlike the Jesus of the Synoptics, the Jesus of John promoted a lifestyle of obedience and submission in light of the authorities of his day.
And I give unto them eternal life; and they shall never perish,
neither shall any man pluck them out of my hand. My Father, which gave
them me, is greater than all; and no man is able to pluck them out of
my Father's hand. I and my Father are one.
— John 10:28-30
If one wants an authentic record of what Jesus actually did and said, the nearest he can come to it is in the Synoptics. The gospel of John, on the other hand, obviously contains more interpretation and mythology than history.
For reasons that go beyond the scope of this question, it is not the Jesus of the Synoptic Gospels but the Jesus of the Gospel of John that carries the greatest weight in how Christians perceive the historical Jesus. However, it is blatantly obvious in any rational approach that the gospel of John is far less reliable as a source on the historical Jesus than the Synoptic Gospels.
