The Dogmatic Constitution Lumen Gentium, approved by the Council on November 19, 1964, tells us about the beauty of the Church, which until then had been seen only as a hierarchical structure. At the top was the Pope, followed by the bishops, the priests, and finally the lay faithful, subject to the authority of the Church’s hierarchy.
Lumen Gentium, on the other hand, states that we must look at the Church as a “mystery” and as the “people of God,” where Baptism assumes great importance as the common denominator of all Christians.
Over the centuries, the aspect of the Church that had emerged with ever greater prominence was its hierarchical structure.
Rather than focusing on its hierarchical structure, which is necessary but gives us only a limited and superficial understanding of the Church, the document states that we must look at the Church as a “mystery” and as the “people of God,” where Baptism assumes great importance as the common denominator of all Christians.

Thus, during the Angelus on October 22, 1995, John Paul II summarized the importance of this document: “The Dogmatic Constitution Lumen Gentium is the ‘keystone’ of all the Council’s teaching. Through it, the Second Vatican Council sought to shed light on the reality of the Church: a wondrous and complex reality, made up of human and divine, visible and invisible elements.

A great merit of Lumen Gentium is that it forcefully reminded us that, if we want to properly grasp the identity of the Church, while not overlooking its institutional aspects, we must begin with its mystery. The Church is a mystery because it is grafted onto Christ and rooted in Trinitarian life. Jesus, the Word of God made man, is the “light” that shines on the face of the Church.”

The Second Vatican Council (1962-1965) produced a total of 16 documents: 4 constitutions, 9 decrees, and 3 declarations.
The next Jubilee, proclaimed by Pope Francis, will take place in 2025 and will have hope as its theme (“Pilgrims of Hope” is the title).
At the Holy Father's request, preparations for this great event in the life of the Church will begin this year, and 2023 will be dedicated to rediscovering the fundamental themes of the four constitutions of the Second Vatican Council.
The Dicastery for Evangelization, in collaboration with Shalom Publishing House, has produced 34 brief study aids, written by experts in language accessible to all, to enable those who are not thoroughly familiar with the Council to discover its teaching. 

Ten volumes of this valuable work are devoted to an in-depth exploration of Lumen Gentium.