The Mass begins with the entrance chant/song. The celebrant and other ministers enter in procession and reverence the altar with a bow and/or a kiss. The altar is a symbol of Christ at the heart of the assembly and so deserves this special reverence.
All make the Sign of the Cross, and the celebrant extends a greeting to the gathered people in words taken from Scripture. This is followed by the Penitential Act where the faithful recall their sins and place their trust in God's abiding mercy. The Penitential Act includes the Kyrie Eleison, a Greek phrase meaning, "Lord, have mercy." This litany recalls God's merciful actions throughout history.
The Gloria follows the Penitential Act. The Gloria begins by echoing the proclamation of the angels at the birth of Christ: "Glory to God in the highest!" In this ancient hymn, the gathered assembly joins the heavenly choirs in offering praise and adoration to the Father and Jesus through the Holy Spirit.
The Introductory Rites conclude with an opening prayer, called the Collect. The celebrant invites the gathered assembly to pray and, after a brief silence, proclaims the prayer of the day. The Collect gathers the prayers of all into one and disposes all to hear the Word of God in the context of the celebration.
Most of the Liturgy of the Word is made up of Readings from Scripture. In the Liturgy of the Word, the Church feeds the people of God from the table of his Word (cf. Sacrosanctum Concilium, no. 51). The Scriptures are the word of God, written under the inspiration of the Holy Spirit. In the Scriptures, God speaks to us, leading us along the path to salvation.
During most of the year, the first reading is from the Old Testament and the second reading is from one of the New Testament letters.
The high point of the Liturgy of the Word is the reading of the Gospel. The Gospel tells of the life, ministry, and preaching of Christ, it receives several special signs of honor and reverence.
The Liturgy of the Eucharist begins with the preparation of the gifts and the altar. The celebrant blesses and praises God for these gifts and places them on the altar, the place of the Eucharistic sacrifice.
The Eucharistic Prayer is the heart of the Liturgy of the Eucharist. In this prayer, the celebrant acts in the person of Christ as head of his body, the Church. He gathers not only the bread and the wine, but the substance of our lives and joins them to Christ's perfect sacrifice, offering them to the Father. The Eucharistic Prayers make clear that these prayers are offered, not to Christ, but to the Father. It is worship offered to the Father by Christ as it was at the moment of his passion, death and resurrection, but now it is offered through the priest acting in the person of Christ, and it is offered as well by all of the baptized, who are part of Christ's Body, the Church. This is the action of Christ's Body, the Church at Mass
"Therefore, O Lord, we humbly implore you…" This "we" signifies that all the baptized present at the Eucharistic celebration make the sacrificial offering in union with Christ and pray the Eucharistic Prayer in union with him. And what is most important, we do not offer Christ alone; we are called to offer ourselves, our lives, our individual efforts to grow more like Christ and our efforts as a community of believers to spread God's Word and to serve God's people, to the Father in union with Christ through the hands of the priest. Most wonderful of all, although our offering is in itself imperfect, joined with the offering of Christ, it becomes perfect praise and thanksgiving to the Father.