Christianity evolved from Judaism some 300 years after the birth of Jesus Christ and the interpretations of later scholars, politicians and religious figures.

It stems from the birth and death of Jesus Christ at which time our modern calendar began with the birth of Jesus being year '0'. However researchers have discovered that it is very likely that Jesus was actually born about six years earlier. (The Gospel of the Essenes)

In addition to the teachings of Jesus, Christianity has its roots in The Bible Old Testament which is a series of stories, histories, myths and legends, some of which may have some truth and others which are pure fantasy.

With the birth of Christ, believing that a man could be born from a virgin birth, be executed and rise again from the dead presents many challenges, but many of his teachings are excellent and by taking his advice, one will progress spiritually.

At the time, Jesus was a spiritual teacher who had a small group of followers from all walks of life and he went about teaching those who would listen about how to create a better life by enriching their spirit and connecting with the divine principal within themselves and nature.

Many people who saw the truth in the teachings of Jesus wrote down what he said and these are the books of the Gnostic Gospels, The Nag Hammadi Library and later the New Testament which also contains interpretations of what Jesus meant and new ideologies presented by the writers seeking to control the growing Christian population for political and social power.

Roman Emperor Constantine
While there is no record of Jesus saying "set up a church in my name",  Christianity became established because the Roman Emperor Constantine established himself as the head of the church around 313 A.D., which made this new "Christianity" the official religion of the Roman Empire.

One of the first things Constantine does, as emperor, is start persecuting other Christians. The Gnostic Christians are targeted...and other dualist Christians. Christians who don't have the Old Testament as part of their canon are targeted. The list of enemies goes on and on. There's a kind of internal purge of the church as one emperor ruling one empire tries to have this single church as part of the religious musculature of his vision of a renewed Rome. And it's with this theological vision in mind that Constantine not only helps the bishops to iron out a unitary policy of what a true Christian believes, but he also, interestingly, turns his attention to Jerusalem, and rebuilds Jerusalem just as a righteous king should do. But what Constantine does is take the city, which was something of a backwater, and he begins to build beautiful basilicas and architecturally ambitious projects in the city itself. The sacred space of the Temple Mount he abandons. It's not reclaimable. And what he does is [to] religiously relocate the center of gravity of the city around the places where Christ had suffered, where he had been buried, or where he [had] been raised. So that in the great basilicas that he built, Constantine has a new Jerusalem, that's splendid and beautiful and... his reputation as an imperial architect resonates with great figures in biblical history like David and Solomon. In a sense, Constantine is a non-apocalyptic Messiah for the church. ...

The bishops are terribly grateful for this kind of imperial attention. It's not the western Middle Ages. The lines of power are unambiguous. Constantine is absolutely the source of authority. And there's no question about that. But the bishops are able to take advantage of Constantine's mood and his curious intellectual interest in things like Christology and the Trinity and Church organization. They're able to have bibles copied at public expense. They are finally able to have public Christian architecture and big basilicas. So there's a comfortable symbiotic relationship between the empire and the church, one that, in a sense, is what defines the cultural powerhouse of Europe and the West.

The first actual Pope in Rome was thought to be Leo I (440-461 A.D.), although some claim that Gregory I was the first (590-604 A.D.). This ungodly system eventually ushered in the darkest period of history known to man, properly known as the "Dark Ages" (500-1500 A.D.). Through popes, bishops, and priests, Satan ruled Europe, and Biblical Christianity became illegal.

Christianity today is diverse with about 35% of the worlds population claimed to be Christian, however many Christians have some very immoral practices. 

The conflict between the Christian and Islamic sects and the attempts to convert from each others congregations is an aggression and a drive for power and wealth.  The more members a sect has, the greater it's wealth and power.

Jesus died at fore the sins of man, and yet today the Christian world still holds him there on the cross dying always for the sins they continue to commit, will Christianity ever get the lesson of Jesus?

Reference books

References
The Legitimisation of Christianity
The Nag Hammadi Library
Anna Kingsford, Clothed with The Sun
Marshall J. Gauvin, The Heart of the Bible