Pope Paul offers a brief “compendium” on the meaning of the Mass.
3. In order to make the indissoluble bond that exists between faith and devotion perfectly clear, the Fathers of the Council decided, in the course of reaffirming the doctrine that the Church has always held and taught and that was solemnly defined by the Council of Trent, to offer the following compendium of truths as an introduction to their treatment of the Most Holy Mystery of the Eucharist:
4. “At the Last Supper, on the night when He was betrayed, our Savior instituted the Eucharistic Sacrifice of His Body and Blood. He did this in order to perpetuate the Sacrifice of the Cross throughout the centuries until He should come again, and so to entrust to His beloved Spouse, the Church, a memorial of His Death and Resurrection: a sacrament of love, a sign of unity, a bond of charity, a paschal banquet in which Christ is eaten, the mind is filled with grace, and a pledge of future glory is given to us.”
The Mass is at once a sacrifice, a sacrament, a sign, a bond, a banquet, and a pledge. That covers a lot of territory.