What actually happens at Mass, step by step?

The Mass is the same sacrifice as Calvary, made present on the altar, and the same meal as the Last Supper (CCC 1362-1372). Every part has a purpose.

Introductory Rites

• Entrance and Sign of the Cross. We gather as the Body of Christ.
• Penitential Act. "I confess..." or "Lord, have mercy." Venial sins are forgiven here.
• Gloria (Sundays outside Advent and Lent). The angels' hymn from Bethlehem.
• Collect. The priest "collects" our prayers into one.

Liturgy of the Word

• First Reading, usually Old Testament (Acts in Easter).
• Responsorial Psalm.
• Second Reading on Sundays, from the New Testament letters.
• Gospel, which we stand for; Christ Himself speaks.
• Homily. The priest or deacon breaks open the Word.
• Creed on Sundays. We profess what we believe.
• Prayer of the Faithful. We pray for the Church, the world, the suffering.

Liturgy of the Eucharist

• Presentation of the gifts. Bread, wine, and our offerings.
• Eucharistic Prayer. The heart of the Mass. The priest, acting in the person of Christ, says "This is my Body... This is my Blood," and the bread and wine become Christ. We kneel. The prayer ends with the Great Amen.
• Our Father, Sign of Peace, Lamb of God.
• Holy Communion. Those in a state of grace receive Christ. Others come for a blessing or pray in the pew.

Concluding Rites

• Blessing and dismissal. "Go forth, the Mass is ended." The word Mass comes from missa, "sending." The point of Mass is to be sent.

Tip for newcomers: follow along in a missal or an app, and do not worry about getting postures right. Nobody is grading. Come early, stay after, and let it work on you.