The following texts are excerpts I've highlighted while reading The General Instruction of the Roman Missal (GIRM). From the Introduction; Testimony of an Unaltered Faith:
The sacrificial nature of the Mass, solemnly defended by the Council of Trent, because it accords with the universal tradition of the Church, was once more stated by the Second Vatican Council, which pronounced these clear words about the Mass: "At the Last Supper, Our Savior instituted the Eucharistic Sacrifice of his Body and Blood, by which the Sacrifice of his Cross is perpetuated until he comes again; and till then he entrusts the memorial of his Death and Resurrection to his beloved spouse, the Church."
..."for whenever the memorial of this sacrifice is celebrated the work of our redemption is accomplished..."
So, in the new Missal the rule of prayer (lex orandi) of the Church corresponds to her perennial rule of faith (lex credendi), by which we are truly taught that the sacrifice of his Cross and its sacramental renewal in the Mass, which Christ the Lord instituted at the Last Supper and commanded his Apostles to do in his memory, are one and the same, differing only in the manner of their offering; and as a result, that the Mass is at one and the same time a sacrifice of praise, thanksgiving, propitiation, and satisfaction.
...the royal Priesthood of the faithful... For the celebration of the Eucharist is the action of the whole Church... For this people is the People of God, purchased by Christ's Blood, gathered together by the Lord, nourished by his word, the people called to present to God the prayers of the entire human family, a people that gives thanks in Christ for the mystery of salvation by offering his Sacrifice, a people, finally, that is brought together in unity by Communion in the Body and Blood of Christ. This people, though holy in its origin, nevertheless grows constantly in holiness by conscious, active, and fruitful participation in the mystery of the Eucharist.
