A Rite represents an ecclesiastical, or church, tradition about how the sacraments are to be celebrated. Each of the sacraments has at its core an essential nature which must be satisfied for the sacrament to be confected or realized. This essence of matter, form and intention derives from the divinely revealed nature of the particular sacrament. It cannot be changed by the Church. Scripture and Sacred Tradition, as interpreted by the Magisterium, tells us what is essential in each of the sacraments (2 Thes. 2:15).
When the apostles brought the Gospel to the major cultural centers of their day the essential elements of religious practice were inculturated into those cultures. This means that the essential elements were clothed in the symbols and trappings of the particular people, so that the rituals conveyed the desired spiritual meaning to that culture. In this way the Church becomes all things to all men that some might be saved (1 Cor. 9:22).
There are three major groupings of Rites based on this initial transmission of the faith, the Roman, the Antiochian (Syria) and the Alexandrian (Egypt). Later on the Byzantine derived as a major Rite from the Antiochian, under the influence of St. Basil and St. John Chrysostom. From these four derive the over 20 liturgical Rites present in the Church today.
A Church is an assembly of the faithful, hierarchically ordered, both in the entire world the Catholic Church, or in a certain territory a particular Church. To be a sacrament (a sign) of the Mystical Body of Christ in the world, a Church must have both a head and members (Col. 1:18). The sacramental sign of Christ the Head is the sacred hierarchy the bishops, priests and deacons (Eph. 2:1922). More specifically, it is the local bishop, with his priests and deacons gathered around and assisting him in his office of teaching, sanctifying and governing (Mt. 28:1920; Titus 1:49). The sacramental sign of the Mystical Body is the Christian faithful. Thus the Church of Christ is fully present sacramentally (by way of a sign) wherever there is a sign of Christ the Head, a bishop and those who assist him, and a sign of Christ's Body, Christian faithful. Each diocese is therefore a particular Church.
The Church of Christ is also present sacramentally in ritual Churches that represent an ecclesiastical tradition of celebrating the sacraments. They are generally organized under a Patriarch, who together with the bishops and other clergy of that ritual Church represent Christ the Head to the people of that tradition. In some cases a Rite is completely coincident with a Church. For example, the Maronite Church with its Patriarch has a Rite not found in any other Church. In other cases, such as the Byzantine Rite, several Churches use the same or a very similar liturgical Rite. For example, the Ukrainian Catholic Church uses the Byzantine Rite, but this Rite is also found in other Catholic Churches, as well as the Eastern Orthodox Churches not in union with Rome.
Finally, the Church of Christ is sacramentally present in the Universal or Catholic Church spread over the entire world. It is identified by the sign of Christ our Rock, the Bishop of Rome, Successor of St. Peter (Mt. 16:18). To be Catholic particular Churches and ritual Churches must be in communion with this Head, just as the other apostles, and the Churches they founded, were in communion with Peter (Gal. 1:18). Through this communion with Peter and his successors the Church becomes a universal sacrament of salvation in all times and places, even to the end of the age (Mt. 28:20).
(google "catholic rites and churches" ewtn)
