What the Catechism of the Catholic Church says on "Purgatory:"
1031. "The Church gives the name Purgatory to this final purification of the elect, which is entirely different from the punishment of the damned. [Cf. Council of Florence (1439): DS 1304; Council of Trent (1563): DS 1820; (1547): 1580; see also Benedict XII, Benedictus Deus (1336): DS 1000.] The Church formulated her doctrine of faith on Purgatory especially at the Councils of Florence and Trent. The tradition of the Church, by reference to certain texts of Scripture, speaks of a cleansing fire. [Cf. 1 Cor 3:15; 1 Pet 1:7.] As for certain lesser faults, we must believe that, before the Final Judgment, there is a purifying fire. He who is truth says that whoever utters blasphemy against the Holy Spirit will be pardoned neither in this age nor in the age to come. From this sentence we understand that certain offenses can be forgiven in this age, but certain others in the age to come. [St. Gregory the Great, Dial. 4, 39: PL 77, 396; cf. Mt 12:32-36.]"
1472. "To understand this doctrine and practice of the Church, it is necessary to understand that sin has a double consequence. Grave sin deprives us of communion with God and therefore makes us incapable of eternal life, the privation of which is called the 'eternal punishment' of sin. On the other hand every sin, even venial, entails an unhealthy attachment to creatures, which must be purified either here on earth, or after death in the state called Purgatory. This purification frees one from what is called the 'temporal punishment' of sin. These two punishments must not be conceived of as a kind of vengeance inflicted by God from without, but as following from the very nature of sin. A conversion which proceeds from a fervent charity can attain the complete purification of the sinner in such a way that no punishment would remain. [Cf. Council of Trent (1551): DS 1712-1713; (1563): 1820.]"
Printed with permission from Catholic Defense.