The Holy Eucharist is unique among the sacraments. Even the variety of names by which it is called emphasized the central position which it occupies in Catholic Christianity. It is the Blessed Sacrament, the Lord's Supper, the Holy of Holies, the Table of the Lord, the Body and Blood of Christ, the Sacrifice of the Mass, Holy Communion, the Sacrament of the Altar, Viaticum, and the Real Presence - to mention only a few of the titles by which the Church has identified this central Mystery of Faith.

Yet among the names that have come down to us, the most favored is the "Eucharist," from the Greek word "Eucharistia," which means "Thanksgiving." It appears already in the writings of St. Ignatius of Antioch (died 107 A.D.) and St. Justin, Martyr (died 165 A.D.)

We may say there are three cardinal mysteries of the Christian religion, namely, the Trinity, the Incarnation, and the Eucharist. Among these the Eucharist implies the other two, since without the Trinity there would have been no Incarnation, and without the Incarnation there would have been no Eucharist. The Eucharist is a Sacrament that is a visible sign instituted by Christ, which effectively produces the grace it signifies. Yet in reflecting on the Eucharist as a sacrament, we must keep in mind what Pope John Paul II said in the first encyclical he wrote as Bishop of Rome.

"The Church lives by the Eucharist, by the fullness of this sacrament, the stupendous content and meaning of which have often been expressed in the Church's magisterium from the most distant times down to our own days......Indeed, the Eucharist is the ineffable sacrament! The essential commitment and, above all, the visible grace and source of  supernatural strength for the Church as the People of God is to persevere and advance constantly in Eucharistic life and Eucharistic piety, and to develop spiritually in the climate of the Eucharist...
With all the greater reason, then, it is not permissible for us, in thought, life, or action to take away from this truly most Holy Sacrament its full magnitude and its essential meaning.
It is at one and the same time a sacrifice-sacrament, a communion-sacrament, and a Presence-sacrament" (The Redeemer of man, IV, 20).

Consequently, although the Eucharist is one sacrament, it is a sacrament in three distinctive ways as sacrifice, communion, and Presence.

Through the Mass, God's mercy makes reparation for the want of divine love that we have shown by committing sin.
Through the Mass, God's mercy removes the guilt of repented venial sins and moves the sinner estranged from Him to return to God.
Through the Mass, God's mercy remits more or less the punishment still due on earth to forgiven sins.
Through the Mass, God's mercy also remits more or less the punishment which the souls in Purgatory have to undergo before entering heaven.

The Mass is a powerful means of petition to God for the graces that we and others need in our pilgrimage through life.

Graces are necessary for the mind to know what is God's will and how it should be fulfilled.
Graces are necessary for the will to desire what pleases God, to choose what He wants us to do, and to sustain our choice by loving Him above all things.

Source: Father John A. Hardon