The soul of a person who dies can go to one of three places. The first is heaven, where a person who dies in a state of perfect grace and communion with God goes. The second is hell, where those who die in a state of mortal sin are naturally condemned by their choice. The intermediate place is purgatory, which is thought to be where most souls go, free of mortal sin, but still in a state of lesser (venial) sin. Purgatory is necessary so that souls can be cleansed and perfected before they enter into heaven. There is scriptural basis for this belief. The primary reference is in 2 Maccabees, 12: 26 and 12: 32. "Turning to supplication, they prayed that the sinful deed might be fully blotted out ... Thus made atonement for the dead that they might be free from sin."
"On this day is observed the commemoration of the faithful departed, in which our common and pious Mother the Church, immediately after having endeavored to celebrate by worthy praise all her children who already rejoice in heaven, strives to aid by her powerful intercession with Christ, her Lord and Spouse, all those who still groan in purgatory, so that they may join as soon as possible the inhabitants of the heavenly city." — Roman Martyrology
The Church, after rejoicing yesterday with those of her children who have entered the glory of heaven, today prays for all those who, in the purifying suffering of purgatory await the day when they will be joined to the company of saints. At no place in the liturgy is stated in more striking fashion the mysterious union between the Church triumphant, the Church militant and the Church suffering; at no time is there accomplished in clearer fashion the twofold duty of charity and justice deriving for every Christian from the fact of his incorporation in the mystical Body of Christ. By virtue of the consoling doctrine of the communion of saints the merits and prayers of each one are able to help all; and the Church is able to join her prayer with that of the saints in heaven and supply what is wanting to the souls in purgatory by means of the Mass and the alms and sacrifices of her children.
The celebration of Mass, the sacrifice of Calvary continued on our altars, has ever been for the Church the principal means of fulfilling towards the dead the great commandment of charity. Masses for the dead are found in the fifth century. But it was St Odilo, fourth abbot of Cluny, who was responsible for the institution of the general commemoration of all the faithful departed; he instituted it and fixed its celebration on November 2nd, the day after All Saints. The practice spread to all of Christendom.
Daily in a special Memento in the Canon of the Mass, at which the priest remembers all those who have fallen asleep in the Lord, the priest implores God to grant them a place of happiness, light and peace. Thus there is no Mass in which the Church does not pray for the faithful departed; but today her thoughts are directed towards them in a particular fashion, with the maternal preoccupation of leaving no soul in purgatory without spiritual aid and of grouping them all together in her intercession. By a privilege that Benedict XV's decree has extended to the whole world every priest can today celebrate three Masses; for the liberation of the souls in purgatory the Church multiplies the offering of the sacrifice of Christ, from which she draws forever on behalf of all her children, infinite fruits of redemption.
The faithful should visit a cemetery to pray for the faithful departed, saying the Lord's Prayer and the Creed (these can be said mentally if deemed more appropriate). The Christian, who must be conscious of and familiar with the idea of death, cannot interiorly accept the phenomenon of the "intolerance of the dead," which deprives the dead of all acceptance in the city of the living. Neither can he refuse to acknowledge the signs of death, especially when intolerance and rejection encourage a flight from reality, or a materialist cosmology, devoid of hope and alien to belief in the death and resurrection of Christ. Such visits should be seen as deriving from the bonds existing between the living and the dead and not from any form of obligation, non-fulfilment of which involves a superstitious fear; membership in a confraternity or other pious association whose objects include "burial of the dead" in the light of the Christian vision of death, praying for the dead, and providing support for the relatives of the dead; suffrage for the dead through alms deeds, works of mercy, fasting, and especially prayers, such as the De profundis, and the formula Requiem aeternam [Eternal Rest], which often accompanies the recitation of the Angelus, the rosary, and at prayers before and after meals. Have family discussions about death, preparing for death, funerals, and the Sacrament of the Sick. Visit the cemetery with those close to you. Visits to the cemetery should be uplifting, calm and peaceful, not a frightening or negative event. Families who go to gravesites should clean them, decorate them, add candles. This can be an all day event, with food and drink. Consult the Directory on Popular Piety and the Liturgy to understand the harmony that piety and devotions must have.