General Catholic
What actually happens during the Mass?
The Mass makes present, in an unbloody sacramental way, the one sacrifice of Christ on Calvary, while also gathering the faithful to hear God's word and receive Christ's own Body and Blood in Holy Communion.
Catholic teaching
The Mass consists of the Liturgy of the Word, where Scripture is proclaimed and explained, and the Liturgy of the Eucharist, where bread and wine become the Body and Blood of Christ and are offered to the Father and received by the faithful, uniting the congregation to Christ's one perfect sacrifice.
Biblical foundation
At the Last Supper, Christ commanded 'do this in remembrance of me' (Luke 22:19) using the sacrificial language of covenant memorial, and Paul explains that 'as often as you eat this bread and drink the cup, you proclaim the Lord's death until he comes' (1 Cor 11:26).
Scripture references
Historical evidence
St. Justin Martyr's detailed description of the Sunday liturgy around AD 155 already includes readings, a homily, prayers of the faithful, the offering of bread and wine, and Holy Communion, showing the essential structure of the Mass has remained remarkably stable for nearly two thousand years.
The Church Fathers
“Bread and wine and water are brought, and the president... offers prayers and thanksgivings... and the people assent, saying Amen.”