Following the prayer of Jesus in the Gospel according to John (17:21-22), it dealt with the relations with the Orthodox Church and other Christian churches. This document reiterated that unity of the two sui juris churches is essential, as well as further dialogue and unity with the Protestant churches.
This document shows that the Roman Catholic Church is officially moved to unity. It has become a common piece of study in ecumenical classes.In paragraph 54, we find the oft-quoted sentence: "In this perspective an expression which I have frequently employed finds its deepest meaning: the Church must breathe with her two lungs!"
In paragraph 79, we see five subjects that are considered important for "more clear" understanding that will bring unity:
1. The relationship between Sacred Scripture, as the highest authority in matters of faith, and Sacred Tradition, as indispensable to the interpretation of the Word of God;
2. The Eucharist, as the Sacrament of the Body and Blood of Christ, an offering of praise to the Father, the sacrificial memorial and Real Presence of Christ and the sanctifying outpouring of the Holy Spirit;
3. Ordination, as a Sacrament, to the threefold ministry of the episcopate, presbyterate and diaconate;
4. The Magisterium of the Church, entrusted to the Pope and the Bishops in communion with him, understood as a responsibility and an authority exercised in the name of Christ for teaching and safeguarding the faith;
5. The Virgin Mary, as Mother of God and Icon of the Church, the spiritual Mother who intercedes for Christ's disciples and for all humanity.
Now that wasn't THAT difficult, was it? Deep, but not difficult.