The Sacrament of Holy Eucharist is the source and summit of the Roman Catholic Church. (Catechism of the Catholic Church 1324). Again, a sacrament is an outward sign, instituted by Jesus Christ, to grant grace.(CCC 1325). Thus, grace is "favor", the free and undeserved help that God gives us to respond to His call to become children of God, adoptive sons and daughters, partakers of the divine nature and of eternal life. (CCC 1996). The term "eucharistein", is a Greek word, that translates to an "action of thanksgiving to God". (CCC 1328). The Sacrament of the Holy Eucharist was instituted at the Lord's Supper, on Holy Thursday, just before Christ's passion. (CCC1328). The Lord took His disciples on the eve of His Passion and because it anticipates the wedding feast of the Lamb in the heavenly Jerusalem. (CCC 1329). The Breaking of the Bread, because Jesus used this rite, part of a Jewish meal, when as master of the table he blessed and distributed the bread, above all at the Last Supper. (CCC 1329). It is by this action that the disciples will recognize Him after His Resurrection in Emmaus and this becomes the expression that the first Christians will use to designate their Eucharistic assemblies. (Luke 24:13-35).
Furthermore, by doing so they signify that all who eat the one broken bread, Christ, enter into Communion with Him and form but one body in Him. (CCC 1329). The signs of Bread and Wine of the Eucharistic celebration, that are transubstantiated by the words of the priest, through the power of the Holy Spirit: "Lord send Your spirit upon these gifts, like the morning dew fall, so that they may become the body and blood of our Lord and Savior, Jesus Christ". (Order of the Mass - Eucharistic Prayer I). On the eve of His Passion, "He took bread...then He took the cup filled it with wine", the signs of bread and wine, surpassing the understanding, the Body and Blood of Christ, for they continue also to signify the goodness of creation. (CCC 1333). Then he took a cup, gave thanks, and said, “Take this and share it among yourselves; for I tell you [that] from this time on I shall not drink of the fruit of the vine until the kingdom of God comes.” Then he took the bread, said the blessing, broke it, and gave it to them, saying, “This is my body, which will be given for you; do this in memory of me.” And likewise the cup after they had eaten, saying, “This cup is the new covenant in my blood, which will be shed for you. (Luke 22: 17-20). For those individuals that have received the Sacrament of Holy Communion, at the time for the Eucharist to be distributed to the assembly attending mass, they will process up to the priest, deacon or Extraordinary Minister of Holy Communion to receive the Body and Blood of Christ. As each person stands before the priest, deacon or Extraordinary Minister of Holy Communion, they hear the words, "the Body of Christ and the Blood of Christ", to which each time they will respond, Amen. It is also custom, to slightly bow or genuflect before receiving the Body and Blood of Christ. For those individuals who have not received the Sacrament of Holy Communion or are not practicing Roman Catholics, they may process in the Communion line and receive a blessing, simply cross your arms across your chest to receive the blessings.
The Sacrament of Holy Communion is quite an extensive topic and could not be explained here in its entirety, one because it remains a mystery of God, an act of faith that requires child-like faith in this efficacious sign. However, one can turn to the Gospel of John 6, to begin the journey of the Holy Eucharist.