This Sacrament has various titles
EUCHARIST: because it is an action of thanksgiving to God. The Greek word eucharistein recalls the Jewish blessings that proclaim God's works: Creation, Redemption, and Sanctification.
THE LORD'S SUPPER: because of its connection with the supper which the Lord took with his disciples on the eve of his Passion and because it anticipates the wedding feast of the Lamb in the heavenly Jerusalem.
THE BREAKING OF BREAD: because Jesus used this rite, part of a Jewish meal, when as master of the table he blessed and distributed the bread (Mt 14), above all at the Last Supper. It is by this action that his disciples will recognize him after his Resurrection (Lk 24:13-35).
THE EUCHARISTIC ASSEMBLY: because the Eucharist is celebrated amid the assembly of the faithful, the visible expression of the church. As St. Augustine would say, "Become what you receive. Receive what you are."
THE HOLY SACRIFICE: because it makes present the one true sacrifice of Christ the Savior, on the cross, and includes the Church's offering. Also referred to as the Unbloody Sacrifice of the Altar.
HOLY COMMUNION: because by this sacrament we unite ourselves to Christ, who makes us sharers in His Body and Blood to form a single body. (I Cor 10:16-17).
The 'Sacrament of Communion' is "the source and summit of the Christian life." It is another step into full initiation of the Catholic Church. Participating in the Eucharist unites us most fully with the Holy Trinity -- God the Father, the Son and the Holy Spirit -- and with one another. We join with Christ and the community of believers in giving thanks and praise to God the Father.
The Eucharist is the memorial of Christ's Passover. It is thanksgiving and praise to God the Father. It is the sacrificial memorial of Christ and his Body. It is the presence of Christ by the power of His word and of His spirit.
This is our Catholic faith. We believe that the bread and wine, offered at Mass, truly become for us the Body and Blood of Christ. The word the Church uses to name this belief is transubstantiation. By the words, '"This is my body.... This cup is the new covenant in my blood," Christ changed the bread and wine of the last supper into His living body and blood -- this is the sacrament of the Holy Eucharist. The bread and wine, though still appearing to be bread and wine, are now Christ Himself.