The Eucharist completes Christian initiation. Through this sacrament of initiation we participate with the whole community of believers in the Lord's own sacrifice. The Eucharist (from the Greek word eucharistia 'thanksgiving') is the sacrament of the body and blood of Christ in which he is present under the forms of bread and wine offering himself in the sacrifice of the Mass and giving himself as spiritual food to the faithful.
At the Last Supper, the Lord instituted the Eucharistic sacrifice of his body and blood. He did this in order to perpetuate the sacrifice of the cross throughout the ages until he should come again, and so to entrust to the church a memorial of his death and resurrection. The Eucharist is the source and summit of the Christian life.