The Holy Sacrifice of the Mass may be offered to God with a fourfold intention: by way of Adoration, Thanksgiving, Petition, and Atonement. It is for the spiritual and temporal welfare of the living, and for the eternal repose of the dead. Every day of the year Holy Mass is offered, except Good Friday.
There are different kinds of Masses: low Mass, read or recited by the priest, high Mass, sung by priest and choir; and solemn high Mass, with deacon and subdeacon assisting the celebrant. These are not really different; they differ only in the elaborateness of the ceremonies used. A pontifical Mass is a high Mass said by a Bishop. A bishop puts on his vestments and takes them off before the altar, unlike the priest, who vests himself in the sacristy.
The purposes for which the Mass is offered are:
To adore God as our Creator.
The Holy Sacrifice of the Mass is the only worthy gift we can offer God; in it we offer to Him His own Son. Having a perfect sacrifice in the Holy Mass, Christians need, and have, no other sacrifice to offer to God but this one.
To thank God for His many favors.
In the Mass Jesus Christ the Son of God speaks for us to His eternal Father; we have an advocate with Him. Can we fail but speak well, having this instrument of thanksgiving?
To ask God to bestow His blessings on all men.
Holy Mass may be offered for the living of whatever creed. It may be offered for departed Catholics. The priest may not offer Mass publicly for departed non-Catholics, but the persons hearing the Holy Mass may do so. Persons hearing Mass have their own private intentions for offering it, aside from the intention of the priest. Holy Mass may be offered for any intention except that which is in itself bad. This petition of God has been greatly distorted with the emphasis in the Novus Ordo of petitions when many times material wants are emphasized over spiritual ones, and in many parishes, can go on as long as there is someone to add in their own petition.
To satisfy the justice of God for the sins committed against Him.
The Holy Sacrifice of the Mass reconciles man with God, as we learn from the words of Christ uttered at the Last Supper, "This is My blood, which is being shed for many unto the forgiveness of sins" (Matthew 26:28). We are not redeemed all over again by the Mass, for we were redeemed once on the cross; but the Holy Sacrifice of the Mass applies to our souls the fruits of redemption gained for us on the cross. As a perfect propitiary sacrifice, the Holy Mass satisfies the justice of God.
By means of the Mass, the fruits of the sacrifice of the cross are applied to our souls.
The sacrifice on the cross - the passion and death of Christ - is the gold mine of graces; Holy Mass is the machinery that takes the gold out for us. At Holy Mass a torrent of graces flows from the altar of God to enrich men. God makes use of other means of grace, such as prayer; but in no other means are graces applied to us so generously.
At Holy Mass we particularly obtain the Grace to repent of mortal sin. It is not necessary to be in the state of grace to hear the Holy Sacrifice of the Mass; the sinner does not commit a fresh sin by doing so; on the contrary he obtains the grace of conversion. Upon the cross Christ cried: "Father forgive them;" at Mass He utters the same prayer on behalf of those present.
There is also forgiveness of venial sins for those who are in the state of grace.
Saint Augustine said that one "Our Father" prayed with devotion would expiate the venial sins of a whole day; how much more effective would be the Holy Sacrifice of the Mass, which is the supreme prayer offered to God!
At Holy Mass we obtain remission of the temporal penalty due to sin.
The penitent thief, who was present at the Sacrifice of the Cross, was quickly admitted into Heaven, with the penalties due his sins all forgiven.
We are sure that our prayers are heard in the Mass, because in it Our Lord Himself prays for us. The fruits of the Mass are granted to the person hearing it devoutly, not only in answer to his prayers, but directly, in virtue of the Sacrifice itself, through which the merits of Christ are applied to his soul.
We may obtain eternal rewards provided we are in the state of grace. We also obtain temporal blessings, such as help in our work, and protection.
The whole Church on earth and in Purgatory participates in the general fruits, for the Holy Sacrifice of the Mass is offered for all, though if they are not in the state of Sanctifying Grace, they will not receive the merits gained. Those who are in the state of grace benefit from the special fruits of the priest who celebrates the Mass,
the per son or persons for whom it is offered, those who serve or assist at the Mass and those for whom the faithful present prayer and offer the Holy Mass in union with the priest.
It's important to note here on the matter of forgiveness and absolution. In the Holy Sacrifice of the Mass perpetuated for all time by Pius V, there has always been two places where we ask forgiveness and receive absolution. The first part is after the entrance prayers of Psalm 42 when the priest recites his Confiteor first, then his Miseratur then our - "I confess" ('Confiteor' recited by the altar boys on behalf of the faithful). Then the Misereatur is repeated again by the celebrant - "May Almighty God have mercy on you, forgive you your sins, and bring you to life everlasting. Amen." Then the priest bestows absolution: Indulgentiam, absolutionem, et remissionem peccatorum nostrorum, tribuat nobis omnipotens et misericors Dominus. Amen. - "May the Almighty and Merciful Lord grant us pardon, absolution, and remission or our sins. Amen." This is repeated after the priest has received the Body and Blood of Christ before the faithful. The acolytes recite the Confiteor and then the celebrant repeats the Miseratur and gives absolution. At both times we make the sign of the cross.
Unfortunately this reconciling act is not found in the "Eucharistic Celebration" concocted by Annibale Cardinal Bugnini and unbelievingly bought and sold by Pope Paul VI and all hierarchy after. In this pseudo Mass it is no longer the priest giving absolution but the congregation acting as the priest by saying "May almighty God have mercy on us, forgive us our sins, and bring us to everlasting life. Amen." This is said only once before the Kyrie and we are forgiving ourselves. Who needs a priest or celebrant in the Novus Ordo? Maybe that's why he's merely called a "presider." These are just a few more cracks that have eroded the sacrificial nature of the Holy Sacrifice of the Mass and passed off today as the "New Mass."