It is significant that many good lay people show such an interest in indulgences - but many priests ignore them. This is true even of good orthodox clergy and, as before, I admit that I was remiss in this for many years.
The Council of Trent defended the doctrine of indulgences but did not give an exposition of the doctrine as it did, for example, on Justification and the Eucharist. Most people remember Pope Paul VI abolished indulgences measured in days or years. It is a pity that he is not also remembered for his fine exposition of the doctrine of indulgences in the Apostolic Constitution Indulgentiarum Doctrina. He reflects on how sin has real consequences, how our good works benefit all because we are united in communion, how the Church developed the practice of dispensing this treasury of merits, and how the Church encourages us to sound piety and works of charity by recommending particular indulgenced prayers and works.
He also outlines how indulgences teach us how sad and bitter it is to have abandoned the Lord God by sin (cf. Jer 2.19), and how closely we are united to each other in Christ. He says that they encourage charity in us, especially when we apply indulgences to those who have died.