Peter's public activity is known chiefly through the New Testament and later Christian tradition. The Gospels portray Simon Peter as a Galilean fisherman called to follow Jesus, a prominent member of the Twelve, and a spokesman among the disciples. He confesses Jesus as the Messiah but also misunderstands his mission and, after the arrest, denies knowing him. These narratives present both authority and failure, making Peter's restoration an important part of the Christian account of discipleship.

Acts describes Peter as a leading figure in the Jerusalem community after the resurrection. At Pentecost he addresses the crowd and calls for repentance and baptism. Subsequent episodes portray him preaching, healing, facing arrest, and explaining the movement's claims before religious authorities. His prominence did not mean that early Christian leadership was organized as a fully developed later church hierarchy. James and other apostles also exercised authority, and the surviving accounts reflect theological aims as well as memories of the community's beginnings.

Peter's role in the inclusion of Gentiles is central to Acts. The account of Cornelius describes him recognizing that non-Jewish believers could enter the community, and the Jerusalem meeting presents him arguing against imposing the full requirements of Jewish law on them. Paul's letter to the Galatians supplies a different contemporary perspective: Paul recalls meeting Cephas, usually identified as Peter, and later challenging him at Antioch over withdrawal from meals with Gentile believers. Together these writings reveal negotiation and disagreement over the boundaries of the movement, rather than a wholly uniform missionary program.

Two New Testament letters bear Peter's name, but their authorship is debated, especially that of 2 Peter. Early Christian traditions associate him with ministry and martyrdom in Rome under Nero; the familiar story of crucifixion upside down comes from later testimony rather than a contemporary report. The precise date and route of his final travels remain uncertain. Catholic teaching regards the bishops of Rome as his successors, while other Christian traditions understand his authority differently. Peter's enduring significance therefore includes the apostolic leadership described in scripture, debates over the admission of Gentiles, and later claims about church authority. A responsible account distinguishes these successive layers of evidence and tradition.