The Mass, the formal, official worship service of Catholicism, is the most important and sacred act of worship in the Catholic Church. Going to Mass is the primary way a Catholic fulfills the Third Commandment to keep holy the Sabbath day and the only regular opportunity to receive the Holy Eucharist. The Mass incorporates the Sacred Scripture, prayer, sacrifice, hymns, symbols, gestures, sacred food for the body and soul, and directions on how to live a Catholic life — all in one ceremony.
The Mass is the unbloody sacrifice of the body and blood of Christ. During the Mass, the bread and wine are changed into the body and blood of Jesus, the Son of God. The Mass is the same sacrifice as that of the Cross, mystically re-presented. The Mass is celebrated to (1) honor and glorify God, (2) to thank Him for all the graces bestowed on the whole world, (3) to satisfy God's justice for the sins of men, and (4) to obtain all graces and blessings.