The document outlines the proceedings and aims of the Second Vatican Council from 1958-1965. It summarizes the key themes of aggiornamento (updating), ressourcement (returning to sources), and development of doctrine. The bulk of the text is the Dogmatic Constitution on the Church "Lumen Gentium" which describes the mystery of the Church, the people of God including the faithful, baptized, non-Christians and non-believers, the hierarchical structure including bishops and the laity, holiness, religious life, and the eschatological nature of the pilgrim Church and its union with the church in heaven. It also covers Mary, Mother of God and her role in salvation history.