I would divide the two thousand years of Christianity into four broad Eras, of about 500 years apiece. This is not just to make it come out even; I think that the characteristics and goals of the Church have gone through four different phases, each of about that long duration. I suspect we are entering, or have entered, a fifth phase, but we have not been long enough into it to describe it.
1. The Age of Definition
The first task of the newly-launched Church was to fully understand who she was, and whom she worshiped. The boundaries demarcating Xtny from Judaism and from paganism had to be fixed. The nature of Christ, both as God and as Man, had to be discovered. The canon of Scripture had to be defined. And so on. With the great Councils, particularly the first four (I Nicaea, I Constantinople, Ephesus, Chalcedon), the whole Church defined her profession of faith.
2. The Age of Fruition
Between c. 500 and 1000, the Church launched out into the World. The society into which she was born was collapsing, but the Church was reaching out to find the farthest peoples she could. In the West, the barbarians who overwhelmed Rome were forming new nations to be reached for Christ; in the East, Russia was evangelized. The rise of Islam cut off expansion to the South and East; when Iceland converted in AD 1000, the farthest reaches of the Western isles then known had been evangelized. Meanwhile, the founding of a parish church in almost every village and neighborhood proceeded apace.
3. The Age of Christendom
Following the East-West schism of 1054, things begin to stagnate. In the West, power struggles and renewal movements typify the Church. The Crusades (East and West) are launched. In the East, the Byzantines struggle to hold off the advancing Turks. Schisms and heresies flourish, as do new religious orders. But increasingly, the Church is stagnant, Christendom like a moated castle under siege.
4. The Age of Separations
The attempt to reform the Church in the West and the resistance thereto led to the breakup we call the Protestant Reformation, the Counter-Reformation, and the Wars of Religion. Where before, it was unthinkable that there should be more than one Church (well, okay, there were "two"), we now had half a dozen, each claiming to be as authentic as could be. Minor sects arose. With the colonization of America and the development of its unique setting of freedom, religious bodies exploded in number. There are today over 750 Christian denominations in North America. And nobody sees anything much odd about this. Tremendous energy has accomplished tremendous good, but nobody has figured out how to put the shattered Church back together.