The largest of the WorldReligions, claiming about 1/3 of the world's population.
The following is quoted from 
A Brief Overview of Christianity:
Christians follow the teachings of and about Yeshua of Nazareth, commonly referred to as Jesus Christ. (Jesus is the Greek form of Yeshua; Christ is Greek for "the Messiah" or the "anointed one.") Yeshua was a Jewish itinerant preacher who was born circa 4 to 7 BCE. He was executed by the Roman occupying authorities in Palestine, perhaps on Friday, 30-APR-7 CE (i.e. in the spring of the year 30). Most Christians regard him as the son of God. They further believe that he is God, the second person in the Trinity. (The Trinity consists of the Father, Son and Holy Spirit; three separate persons, all eternal, all omnipresent, who form a single, unified deity.) Most Christians believe that Jesus co-existed with God before the creation of the world, was born of a virgin, was resurrected three days after his death, and later ascended to Heaven.
The followers of Yeshua formed the Jewish Christian movement, centered in Jerusalem, after his death. They regarded themselves as a reform movement within Judaism; they continued to sacrifice at the temple, circumcise their male children, follow Jewish kosher food laws, etc. Saul of Tarsus, originally a persecutor of the Jewish Christians, reported having a vision of the risen Christ. Adopting the new name of Paul, he became the greatest theologian of the early Christian movement. His writings, along with those of the author(s) of the Gospel of John, provided much of the theological foundation for Christianity as we know it. Paul's ministry was directed to Gentiles -- non-Jews in the Mediterranean basin. After the destruction of Jerusalem by the Roman Army in 70 CE, the Jewish Christian movement was largely dissipated, leaving Pauline Christianity among the Gentiles as the dominant group.
The Roman Empire recognized Pauline Christianity as a valid religion in 313 CE. Later in that century, it became the official religion of the Empire. Church authority became concentrated among the five bishops or patriarchs located in Alexandria, Antioch, Constantinople, Jerusalem and Rome. With the expansion of Islam throughout the Middle East during the seventh century CE, power became concentrated in Constantinople and Rome. These two Christian centers gradually grew apart in belief, and practice. In 1054 CE, a split was formalized between the Roman Catholic and Eastern Orthodox churches; it remains in effect today.
The Protestant Reformation in the 16th century led to a split within the western church. The Protestant movement further fragmented into what is now thousands of individual denominations and groups of denominations.
Christian beliefs about one's destination after death vary greatly:
About 33% of the world's population regard themselves as Christian. This percentage has been stable for decades. (The second most popular religion is Islam at about 20%. It is growing. If its present growth rate continues, it will to become the dominant religion of the world during in a few decades.) About 75% of American adults and a similar number of Canadians identify themselves as Christian. This number has recently been dropping about one percentage point per year. This is mainly due to:
Christianity in North America is a severely divided faith, consisting of over 1,000 denominations, which are often categorized into conservative, mainline and liberal wings:
Interesting factoid from the Religious Tolerance site:
See other InterestingReligions.