“The holy Eucharist completes Christian initiation. Those who have been raised to the dignity of 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. “At the Last Supper, on the night he was betrayed, our Savior instituted the Eucharistic sacrifice of his Body and Blood. This he  did in order to perpetuate the sacrifice of the cross throughout the ages until he should come again, and so to entrust to his beloved Spouse, the Church, a memorial of his death and resurrection: a sacrament of love, a sign of unity, a bond of charity, a Paschal banquet ‘in which Christ is consumed, the mind is filled with grace, and a pledge of future glory is given to us.’”
“The Eucharist is “the source and summit of the Christian life.”

CCC 1322-1324

The culmination of the sacraments of initiation – indeed, of all the sacraments – is the Eucharist.  The word “eucharist” means “thanksgiving”.  In the Eucharist, Christ – through the agency of the priest – transforms ordinary bread and wine into his full being:  body, blood, soul, and divinity.  Although the outward appearances of the bread and wine do not change, the underlying reality, the actual substance of the bread and wine completely and totally ceases to exist.  They are completely and totally replaced with the substance of Christ’s own Body and Blood.  This change is called Transubstantiation and occurs when, only by the power of Christ, the priest utters the words of consecration:  “This is my body . . . This is my blood.” These are the very words that Christ empowered the apostles and their successors to speak when he instructed them at the Last Supper to “Do this in memory of me.”

Christ instituted the Eucharist to provide us spiritual nourishment.  The bread and wine are the signs or symbols of the spiritual nourishment that we receive.  When we receive physical food, like bread and wine, it becomes part of our physical bodies.  When we receive the Eucharist, the underlying reality of Christ’s presence becomes a part of our spiritual selves. We are united with Christ in a close and personal union.  In the greatest of all of the undeserved gifts that we receive from God, we are joined with His son.