The Catechism of the Catholic Church (CCC) discusses the Eucharist as one of the 3 sacraments of initiation, along with Baptism and Confirmation. In #1322, the CCC teaches that the Eucharist “completes Christian initiation.” (In many parts of the world, including much of the United States, our Church still delays Confirmation until after reception of First Eucharist, creating a very bizarre contradiction between teaching and practice.) “Those who have been raised to the royal priesthood by Baptism and configured more deeply to Christ by Confirmation participate with the whole community in the Lord’s own sacrifice by means of the Eucharist.” (CCC, #1322).
The CCC goes on to teach that the Eucharist is “’the source and summit of the Christian life’”, quoting the Constitution on the Church from the Second Vatican Council (#1324). The celebration of the Eucharist “is the sign and sublime cause of that communion in the divine life and that unity of the People of God by which the Church is kept in being” (#1325). The Eucharistic celebration also unites the Church on earth “with the heavenly liturgy and anticipates eternal life, when God will be all in all” (#1326).
Notice that the CCC first talks about the royal priesthood of the entire believing community that exists because of Baptism, and that the Eucharist is the means by which that royal priesthood is sustained, nourished, energized, and sent on mission.
The CCC then goes on to comment on the various names given to the sacrament of the Eucharist: 1) Eucharist (because it is an action of thanksgiving to God, recalling the Jewish blessings “that proclaim – especially during a meal – God’s works: creation, redemption, and sanctification” (#1326); 2) The Lord’s Supper and the Breaking of Bread, recalling the two biblical bases of the sacrament (the Last Supper, and the meal at Emmaus in the Gospel according to Luke 24:13-35), as well as the Eucharistic assembly, “because the Eucharist is celebrated amid the assembly of the faithful, the visible expression of the Church” (#1329).
Other names, such as the memorial of the Lord’s Passion and Resurrection, the Holy Sacrifice, the Holy and Divine Liturgy, Holy Communion, and Holy Mass, are then briefly mentioned and commented upon (#s 1330-1332).
These different names for the sacrament indicate that the Eucharistic celebration is indeed a sacred mystery – not an experience that we cannot at all understand, but an experience that is so rich and deep that any one or several names do not completely exhaust its meaning or significance. The example I like to use for such a “mystery” is that it is like looking into a locked room through a window in the door that allows us to see some, maybe most, but not all of what is in the room. We can see and know some of what is in the room, but there will always some areas and objects that cannot be seen. Other such “mysteries” in our faith are the Trinity, Christ himself, the Church, and the sacraments, to name a few – I would include the Bible as one of those “mysteries” as well.
So the Eucharist is (to use another metaphor) an inexhaustible fountain, an experience of spiritual unity and nourishment that never runs dry for the royal priesthood of the baptized who celebrate it.