Christianity is an Abrahamic monotheistic religion based on the life and teachings of Jesus of Nazareth. Its adherents, known as Christians, believe that Jesus Christ is the Son of God and savior of all people, whose coming as the Messiah was prophesied in the Old Testament and chronicled in the New Testament. It is the world's largest religion with over 2.4 billion followers.Christianity began as a Second Temple Judaic sect in the 1st century in the Roman province of Judea. Jesus' apostles, and their followers, spread it around Syria, Europe, Anatolia, Mesopotamia, Transcaucasia, Egypt, Ethiopia, and Asia, despite initial persecution. It soon also attracted Gentile God-fearers, which lead to a departure from Jewish customs, and the establishment of Christianity as an independent religion. Emperor Constantine the Great converted to Christianity and decriminalized it in the Roman Empire by the Edict of Milan (313), later convening the Council of Nicaea (325) where Early Christianity was consolidated into what would become the state church of the Roman Empire (380). The early history of Christianity sometimes referred to as the Great Church, the united communion of the "orthodox" Christian churches before their schisms. Oriental Orthodoxy split after the Council of Chalcedon (451) over differences in Christology, while the Eastern Orthodox Church and the Catholic Church separated in the East–West Schism (1054), especially over the authority of the Bishop of Rome. Similarly, Protestantism split in numerous denominations from the Catholic Church in the Protestant Reformation (16th century) over theological and ecclesiological disputes, most predominantly on the issue of justification and papal primacy. Following the Age of Discovery (15th–17th century), Christianity was spread into the Americas, Oceania, sub-Saharan Africa, and the rest of the world via missionary work.Christianity remains culturally diverse in its Western and Eastern branches, as well as in its doctrines concerning justification and the nature of salvation, ecclesiology, ordination, and Christology. The four largest branches of Christianity are the Catholic Church (1.3 billion), Protestantism (920 million), the Eastern Orthodox Church (260 million) and Oriental Orthodoxy (86 million), amid various efforts toward ecumenism Their theology and professions of faith, in addition to the Bible, generally hold in common that Jesus suffered, died, was buried, descended into the grave and rose from the dead to grant eternal life to those who believe in him for the forgiveness of their sins. His incarnation, earthly ministry, crucifixion and resurrection are often referred to as the gospel, meaning the "good news". Describing Jesus' life and teachings are the four canonical gospels of Matthew, Mark, Luke and John, with the Jewish Old Testament as the Gospel's respected background. Christianity and Christian ethics played a prominent role in the development of Western civilization, particularly around Europe during late antiquity and the Middle Ages. Despite a decline in membership in the West, Christianity remains the dominant religion in the region, with more than 70% of the population identifying as Christian. Christianity is growing rapidly in Africa and Asia, the world's most populous continents..