The Purgatory, the final purification of Souls
The Compendium of the Catechism of the Catholic Church, first published in 2005, is a summary in dialogue form of the Catechism of the Catholic Church. It deals with purgatory in the following exchange:
210. What is purgatory?
Purgatory is the state of those who die in God’s friendship, assured of their eternal salvation, but who still have need of purification to enter into the happiness of heaven.
211. How can we help the souls being purified in purgatory?
Because of the communion of saints, the faithful who are still pilgrims on earth are able to help the souls in purgatory by offering prayers in suffrage for them, especially the Eucharistic sacrifice. They also help them by almsgiving, indulgences, and works of penance.