The Second Vatican Council (1962-1965) was the 21st ecumenical council of the Catholic Church, convened by Pope John XXIII and concluded under Pope Paul VI. It was the most significant event in the Catholic Church in the 20th century, attended by over 2,600 bishops from around the world. Vatican II produced 16 documents that renewed and updated Church life while preserving essential doctrine. Key changes included: (1) The Mass could be celebrated in the vernacular (local language) rather than exclusively in Latin. (2) Greater emphasis on the role of the laity in the Church. (3) Affirmation of religious liberty as a human right (Dignitatis Humanae). (4) Openness to ecumenical dialogue with other Christians and interreligious dialogue with non-Christians (Nostra Aetate). (5) A renewed emphasis on Scripture in Catholic life (Dei Verbum). (6) The Church described as the 'People of God,' not just a hierarchical institution (Lumen Gentium). Vatican II did not change any dogma; it was a pastoral council aimed at engaging the modern world (Gaudium et Spes) while remaining faithful to Sacred Tradition.