The early Church was born at Pentecost when the Holy Spirit descended upon the apostles and disciples of Jesus, transforming them from hiding in fear to going out into the world to spread the gospel message. Led by figures like Paul of Tarsus, the Church grew rapidly throughout the Roman Empire in the first centuries AD despite periods of persecution. Key events like the Councils of Jerusalem and Nicea helped establish unity in the face of theological disputes and diversity within the early Christian community.