The Church - mystery of men's union with God
In the Church this communion of men with God, in the "love [that] never ends," is the purpose which governs everything in her that is a sacramental means, tied to this passing world.
"[The Church's] structure is totally ordered to the holiness of Christ's members. And holiness is measured according to the 'great mystery' in which the Bride responds with the gift of love to the gift of the Bridegroom." Mary goes before us all in the holiness that is the Church's mystery as "the bride without spot or wrinkle." This is why the "Marian" dimension of the Church precedes the "Petrine."
Source: Catechism of the Catholic Church (Vatican.va)