The richness and importance of the Lord's Supper in Christianity are conveyed by the various names given to it. It has been called both a sacrament and an ordinance of Christ. In terms of its origin in history, it is called "the Last Supper"; as an act of thanksgiving by the church, it is called the Eucharist (from Gk. eucharistein/eulogein) and the Eucharistic Assembly (synaxis); from its Jewish-Christian origins, it is the Breaking of Bread and the Memorial of the Lord's passion and resurrection; in patristic development, it is the Holy Sacrifice because it mysteriously makes present the one, unique sacrifice of Christ and includes the church's offering; also it is the Holy and Divine Liturgy because the whole worship of the church finds its center in the celebration of this Sacred Mystery. Within the liturgy it is called the bread of angels and bread from heaven and the medicine of immortality. It is also Holy Communion since it is union with Christ. Finally, since the liturgy ends with the sending forth (Latin missio) of the faithful to fulfill God's will in their lives, it is called "the Mass."
The New Testament both describes its institution by the Lord Jesus and refers to its actual implementation and celebration by the church. Further, the New Testament sets the context for the institution of the Last Supper by an emphasis on table fellowship. Jesus was both the guest at (Luke 5:29-32, 7:36-50) and the host at meals during his ministry (Mark 2:15). Further, the feeding miracles of Jesus (Mark 6:31-44, 8:1-11 ) point not only to shared fellowship but also to the future "messianic banquet" (see Isa 25:6-12). Jesus spoke of meals and joyous banquets in his parables (e.g., Matt 22:1-14; Luke 14:15-24). Further, according to Luke, the disciples "ate and drank with him after he rose from the dead" (Acts 10:41; cf. Luke 14:30).
The key theological elements of the Lord's Supper as it was celebrated in the early church are: (1) the proclamation of the death of Jesus through "memorial" and "remembrance" and a sacrifice of praise and thanksgiving; (2) the inauguration of the new covenant in the sacrificial blood of Jesus; (3) the participation and fellowship in Christ unto the Father, and with one another in Christ; (4) the experiencing the firstfruit of the joy of the eschatological kingdom of God; (5) the presence of the Spirit of the Father to vivify; and (6) the presence of faith, which is faithful and obedient, in the hearts of believers.
Adapted from "the lord's supper" in the baker's evangelical dictionary of biblical theology.