Christianity is centered on the person of Jesus. He was born during a time of great religious and political unrest in Israel under Roman domination. The Jews were splintered into groups that advocated widely divergent responses to the times. Many believed they were living in the "end times" and expected God to intervene in a dramatic way, which would include the appearance of a leader called the Messiah. Jesus' ministry of teaching and healing probably began in his late twenties and lasted no more than three years. He was arrested in Jerusalem at Passover time by authorities who considered him a threat. He was soon tried and executed by crucifixion on a cross. Three days after he was buried, his followers found an empty tomb. Others reported appearances and visitations by a transformed Jesus that had been resurrected from the dead. Christian scriptures say that forty days later he ascended to the heavens, promising to return again.

Virtually all we know of Jesus comes by way of the four Gospels in the New Testament that describe the life and teachings of Jesus. These portraits of Jesus were recorded some time after his death and reflect the distinctive viewpoints and culture of the individual writers. Jesus is portrayed as a Jew accepting the practices and authority of his tradition. Noted for independence of thought, Jesus centers his teaching on the subject of the Kingdom of God. He emphasizes love for God and other people. He recommends not judging others, compassion, help for the needy and oppressed, forgiveness, and nonviolence. He urges simplicity and is wary of overly strict observance of laws when they hurt people.

Paul is responsible for the spread of belief in Jesus beyond the Jewish world through his extensive travels, powerful letters, and incisive thinking. Through his prompting and leadership, the early church decided that converts did not have to observe Jewish religious laws. In Paul's view, a right relationship with God came only through faith in Jesus. Following moral rules was done willingly out of gratitude for what God had accomplished through Jesus' sacrifice on the cross. Essentially, Paul's views on the meaning of Jesus, morality, and Christian practice became the norm for most of the Christian world.

The Christian worldview took many centuries to be fully worked out through discussions, controversies, and great councils that produced the central creeds of the faith. The Holy Trinity is the belief that God, although one, is three "persons." The Father is the guiding intelligence that created the universe and made human beings an important part of the divine cosmic plan. The Son is Jesus Christ, who has both a fully human and a fully divine nature united in one person. The Holy Spirit is the power of God that guides all believers. Christians believe in life after death, a resurrection of all people, and a final judgment that will lead to an eternal life in either a joyous heaven or a torturous hell, depending on one's faith and goodness in the eyes of God.

In the Middle Ages, Christianity developed thriving monastic and mystical movements and produced great figures such as Francis of Assisi. Controversies over doctrine and church structure led to schisms that produced the great branches of Eastern Orthodox, Roman Catholic, and Protestant Christianity—with Protestantism itself subdividing many more times.

Christian practice is rich, complex, and varied in the different branches. All Christians practice baptism and observe the Lord's Supper, with varying understandings. Holidays that mark significant times in the life of Christ and the early church, such as Easter and Christmas, are celebrated. Christianity has had a profound effect on the arts in the fields of architecture, painting, sculpture, and music. Its themes and stories are echoed in much great literature. Christianity continues to affect history and has in turn faced challenges from the modern world, especially with the growth of science and the changing roles of women.