The ecclesiology of Vatican II centers on "communio", the vital union of each member of the Church with Christ, and of all with one other in Christ. As a more concrete way of expressing this "communio", the Council dwells on the expression "People of God".
1. The sacramental nature of the Church.
It is common to speak of the "mystery of the Church". "Mystery" in a religious sense does not imply something closed and inaccessible, but rather a reality so deep that we can always discover more to its meaning without ever exhausting it. The Church is more than she appears, and the key to grasping her full reality is faith; "it is only 'with the eyes of faith' that one can see her in her visible reality and at the same time in her spiritual reality as bearer of divine life" (CCC 770).
The Church as Teacher - "Magister" - hands on the doctrine of salvation to each generation. Her "Magisterium" or teaching office is exercised when, in the name of Jesus and with his presence and protection, she teaches truths which need to be believed and practised (faith and morals) if one is to get to heaven: "Go and make disciples of all nations..., teaching them to observe all that I have commanded you; I am with you always, to the close of the age" (Mt 28:18-20); "He who believes and is baptized will be saved; but he does not believe will be condemned" (Mk 16:15-16).
The Church cannot be understood just by examining her visible elements. An institution, the Church is particularly a living organism, with spiritual and mystical dimensions which are much more important than any human analysis reveals.
"The Church is the Body of Christ. Through the Spirit and his action in the sacraments, above all the Eucharist, Christ, who once was dead and is now risen, establishes the community of believers as his own Body" (CCC 805).