A Christian holds a cross as she takes part with others in a procession to re-enact the crucifixion of Jesus Christ on the occasion of Good Friday celebrations in India. (Credit: Arun Sankara/AFP/Getty Images)
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Introduction

Christianity is the most widely practiced religion in the world, with more than 2 billion followers. The Christian faith centers on beliefs regarding the birth, life, death and resurrection of Jesus Christ. While it started with a small group of adherents, many historians regard the spread and adoption of Christianity throughout the world as one of the most successful spiritual missions in human history.

Some basic Christian concepts include:

  • Christians are monotheistic, i.e., they believe there’s only one God, and he created the heavens and the earth. This divine Godhead consists of three parts: the father (God himself), the son (Jesus Christ) and the Holy Spirit.
  • The essence of Christianity revolves around the life, death and Christian beliefs on the resurrection of Jesus. Christians believe God sent his son Jesus, the messiah, to save the world. They believe Jesus was crucified on a cross to offer the forgiveness of sins and was resurrected three days after his death before ascending to heaven.
  • Christians contend that Jesus will return to earth again in what’s known as the Second Coming.
  • The Holy Bible includes important scriptures that outline Jesus’s teachings, the lives and teachings of major prophets and disciples, and offer instructions for how Christians should live.
  • Both Christians and Jews follow the Old Testament of the Bible, but Christians also embrace the New Testament.
  • The cross is a symbol of Christianity.
  • The most important Christian holidays are Christmas (which celebrates the birth of Jesus) and Easter (which commemorates the resurrection of Jesus).

Most historians believe that Jesus was a real person who was born between 2 B.C. and 7 B.C. Much of what scholars know about Jesus comes from the New Testament of the Christian Bible.

According to the text, Jesus was born to a young Jewish virgin named Mary in the town of Bethlehem, south of Jerusalem in modern-day Palestine. Christians believe the conception was a supernatural event, with God impregnating Mary via the Holy Spirit.

Very little is known about Jesus’s childhood. Scriptures reveal that he grew up in Nazareth, he and his family fled persecution from King Herod and moved to Egypt, and his “earthly” father, Joseph, was a carpenter.

Jesus was raised Jewish, and according to most scholars, he aimed to reform Judaism—not create a new religion.

When he was around 30 years old, Jesus started his public ministry after being baptized in the Jordan River by the prophet known as John the Baptist.

For about three years, Jesus traveled with 12 appointed disciples, teaching large groups of people and performing what witnesses described as miracles. Some of the most well-known miraculous events included raising a dead man named Lazarus from the grave, walking on water and curing the blind.

Jesus used parables—short stories with hidden messages—in his teachings.

Some of the main themes that Jesus taught, which Christians later embraced, include:

  • Love God.
  • Love your neighbor as yourself.
  • Forgive others who have wronged you.
  • Love your enemies.
  • Ask God for forgiveness of your sins.
  • Jesus is the Messiah and was given the authority to forgive others.
  • Repentance of sins is essential.
  • Don’t be hypocritical.
  • Don’t judge others.
  • The Kingdom of God is near. It’s not the rich and powerful—but the weak and poor—who will inherit this kingdom.

In one of Jesus’s most famous speeches, which became known as the Sermon on the Mount, he summarized many of his moral instructions for his followers.

Many scholars believe Jesus died between 30 A.D. and 33 A.D., although the exact date is debated among theologians.

According to the Bible, Jesus was arrested, tried and condemned to death. Roman governor Pontius Pilate issued the order to kill Jesus after being pressured by Jewish leaders who alleged that Jesus was guilty of a variety of crimes, including blasphemy.

Jesus was crucified by Roman soldiers in Jerusalem, and his body was laid in a tomb. According to scripture, three days after his crucifixion, Jesus’s body was missing.

In the days after Jesus’s death, some people reported sightings and encounters with him. Authors in the Bible say the resurrected Jesus ascended into Heaven.

The Christian Bible is a collection of 66 books written by various authors. It’s divided into two parts: The Old Testament and the New Testament.

The Old Testament, which is also recognized by followers of Judaism, describes the history of the Jewish people, outlines specific laws to follow, details the lives of many prophets, and predicts the coming of the Messiah.

The New Testament was written after Jesus’s death. The first four books—Matthew, Mark, Luke and John—are known as the “Gospels,” which means “good news.” These texts, composed sometime between 70 A.D. and 100 A.D., provide accounts of the life and death of Jesus.

Letters written by early Christian leaders, which are known as “epistles,” make up a large part of the New Testament. These letters offer instructions for how the church should operate.

The Acts of the Apostles is a book in the New Testament that gives an account of the apostles’ ministry after Jesus’s death. The author of Acts is the same author as one of the Gospels—it is effectively “part two” to the Gospels, what happened after Jesus’s death and resurrection.

The final book in the New Testament, Revelation, describes a vision and prophecies that will occur at the end of the world, as well as metaphors to describe the state of the world.

According to the Bible, the first church organized itself 50 days after Jesus’s death on the Day of Pentecost—when the Holy Spirit was said to descend onto Jesus’s followers.

Most of the first Christians were Jewish converts, and the church was centered in Jerusalem. Shortly after the creation of the church, many Gentiles (non-Jews) embraced Christianity.

Early Christians considered it their calling to spread and teach the gospel. One of the most important missionaries was the apostle Paul, a former persecutor of Christians.

Paul’s conversion to Christianity after he had a supernatural encounter with Jesus is described in Acts of the Apostles. Paul preached the gospel and established churches throughout the Roman Empire, Europe and Africa.

Many historians believe Christianity wouldn’t be as widespread without the work of Paul. In addition to preaching, Paul is thought to have written 13 of the 27 books in the New Testament.

Early Christians were persecuted for their faith by both Jewish and Roman leaders.

In 64 A.D., Emperor Nero blamed Christians for a fire that broke out in Rome. Many were brutally tortured and killed during this time.

Under Emperor Domitian, Christianity was illegal. If a person confessed to being a Christian, he or she was executed.

Starting in 303 A.D., Christians faced the most severe persecutions to date under the co-emperors Diocletian and Galerius. This became known as the Great Persecution.

When Roman Emperor Constantine converted to Christianity, religious tolerance shifted in the Roman Empire.

During this time, there were several groups of Christians with different ideas about how to interpret scripture and the role of the church.

In 313 A.D., Constantine lifted the ban on Christianity with the Edict of Milan. He later tried to unify Christianity and resolve issues that divided the church by establishing the Nicene Creed.

Many scholars believe Constantine’s conversion was a turning point in Christian history.

In 380 A.D., Emperor Theodosius I declared Catholicism the state religion of the Roman Empire.

The Pope, or Bishop of Rome, operated as the head of the Roman Catholic Church.

Catholics expressed a deep devotion for the Virgin Mary, recognized the seven sacraments, and honored relics and sacred sites.

When the Roman Empire collapsed in 476 A.D., differences emerged among Eastern and Western Christians.

In 1054 A.D., the Roman Catholic Church and the Eastern Orthodox church split into two groups.

Between about 1095 A.D. and 1230 A.D., the Crusades, a series of holy wars, took place. In these battles, Christians fought against Muslims to reclaim holy land in the city of Jerusalem.

The Christians were successful in occupying Jerusalem during some of the Crusades, but they were ultimately defeated.

After the Crusades, the Catholic Church’s power and wealth increased.

In 1517, a German monk named Martin Luther published 95 Theses—a text that criticized certain acts of the Pope and protested some of the practices and priorities of the Catholic church.

Later, Luther publicly said that the Bible didn’t give the Pope the sole right to read and interpret scripture.

Luther’s ideas triggered the Reformation—a movement that aimed to reform the Catholic church. As a result, Protestantism was created, and different denominations of Christianity eventually began to form.

Christianity is broadly split into three branches: Catholic, Protestant, and (Eastern) Orthodox.

The Catholic branch is governed by the Pope and Catholic Bishops around the world. The Orthodox (or Eastern Orthodox) is split into independent units each governed by a Holy Synod; there is no central governing structure akin to the Pope.

There are numerous denominations within Protestant Christianity, many of which differ in their interpretation of the Bible and understanding of the church.

Some of the many denominations that fall under the category of Protestant Christianity include:

  • Baptist
  • Episcopalian
  • Non-Denominational
  • Evangelist
  • Methodist
  • Presbyterian
  • Pentecostal/Charismatic
  • Lutheran
  • Anglican
  • Evangelical
  • Assemblies of God
  • Christian Reform/Dutch Reform
  • Church of the Nazarene
  • Disciples of Christ
  • United Church of Christ
  • Mennonite
  • Christian Science
  • Quaker
  • Seventh-Day Adventist

Although the many sects of Christianity have differing views, uphold separate traditions, and worship in distinct ways, the core of their faith is centered around the life and teachings of Jesus.

Christianity Fast Facts. CNN.
The Basics of Christian History. BBC.
Christianity. BBC.
Death and Resurrection of Jesus. Harvard Divinity School.
Life and Teachings of Jesus. Harvard Divinity School.
Legitimization Under Constantine. PBS.