Catholics use the word Mass to describe the Eucharistic celebration. The Catechism of the Catholic Church (CCC) defines the word "church" as, " CCC paragraph 751 - The word "church" (Latin ecclesia, from the Greek "ek-ka-lein" to "call") means an assembly or convocation. It designates the assemblies of the people, usually for a religious purpose. “Ekklesia” is frequently used in the Greek Old Testament for the assembly of the Chosen People before God, above all for their assembly on Mount Sinai where Israel received the Law and was established by God as his holy people. By calling itself "Church," the first community of Christian believers recognized itself as heir to that assembly. In the Church, God is "calling together" his people from all the ends of the earth. The equivalent Greek term Kyriake, from which the English word Church and the German Kirche are derived, means "what belongs to the Lord." “CCC paragraph 777 - The word "Church" means "convocation." It designates the assembly of those whom God's Word "convokes," i.e., gather together to form the People of God, and who themselves, nourished with the Body of Christ, become the Body of Christ.” To Catholics, "church" refers to the entire assembly of people, rather than just the liturgical and eucharistic celebration.
For Catholics, the Church (the assembly of Christians) is the bride of Christ as written in Ephesians 5:21-33, that our relationship with Christ should be the same relationship one should have with a spouse. It is a relationship filled with love and respect. Like a marriage, two people become “one body.” When a husband loves his wife, he “loves himself and cares for his ‘own flesh.’
The Mass is the liturgical and Eucharistic celebration that Catholics celebrate daily. The word "Mass" comes from the Latin phrase “Ite missa est." Those are the words used at the end of the liturgical celebration. This phrase, which means "Go, it is the dismissal," eventually became associated with the entire celebration itself and gave rise to the word Mass.
How do we best explain what the Mass is? The Venerable Fulton Sheen explained the Mass as “We shall find Calvary renewed, re-enacted, re-presented, as we have seen, in the Mass. Calvary is one with the Mass, and the Mass is one with Calvary, for in both there is the same Priest and Victim. The Seven Last Words are like the seven parts of the Mass. And just as there are seven notes in music admitting an infinite variety of harmonies and combinations, so too on the Cross there are seven divine notes, which the dying Christ rang down the centuries, all of which combine to form the beautiful harmony of the world’s redemption”. Venerable Fulton J. Sheen, Calvary, and the Mass [1936]
The structure of the Mass has evolved. The Mass is an inspirational act of worship. To fully appreciate the Mass, you must understand its history. The Mass has its roots in the Jewish Passover meal at the Last Supper. In Matthew 26:26-30, Jesus teaches the apostles how to celebrate the Mass, using Sacred Scriptures. The Mass is a celebration that the Church has observed since ancient times. It allows participants to remember and partake in the Last Supper, as well as the passion, death, and resurrection of Jesus Christ.