The eventual outcome was to describe God as three hypostases (three persons) in one ousia (essence). Tertullian, a theologian from Carthage, had already suggested a Latin version: “three persons and one substance”.
This Council finalised the creed we call the Nicene Creed, (what some churches call the Nicene-Constantinople Creed), a creed used by both the Western and Eastern churches.
Meanwhile the Western church was beginning to finalise the shape the Apostles’ Creed (the Eastern church never used it). This creed probably began as a baptism creed, hence “I believe...”
The Nicene Creed was a creed of the whole church (“We...”) and served to clarify what the church throughout the world believed, in contrast to the groups who believed heresies. That is what “catholic” means. It is the whole church throughout the world that believes the orthodox teachings of the Bible.
Later “Roman Catholic” referred to the Western church centred in Rome as distinct from the “Eastern Orthodox” church centred in Constantinople. In these two titles, “catholic” and “orthodox” have similar meanings.
Dale