The origins of the Eucharist are found in the Last Supper that Jesus shared with his Apostles. "In order to leave them a pledge of this love, in order never to depart from his own and to make them sharers in his Passover, he instituted the Eucharist as the memorial of his death and Resurrection and commanded his apostles to celebrate it until his return; 'thereby he constituted them priests of the New Testament'" (CCC, no. 1337, citing Council of Trent: DS 1740).
So rich is this mystery that we have a number of terms to illumine its saving grace: the Breaking of the Bread; the Lord's Supper; the Eucharistic Assembly; the Memorial of Christ's Passion, Death, and Resurrection; the Holy Sacrifice of the Mass, the Holy and Divine Liturgy; the Eucharistic Liturgy; Holy Communion; and Holy Mass (d. CCC, nos. 1328-1332).
~ From the United States Catholic Catechism for Adults