Father Tom Margevicius, the director of worship in the Archdiocese of St. Paul and Minneapolis, offers the following explanation of an indulgence.

The Catechism of the Catholic Church teaches 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.”

Just as the sacrament of reconciliation removes the eternal punishment of sin by sacramental absolution, so too an Indulgence removes the temporal punishment of sin. The word “indulgence” comes from the Latin “indulgere,” meaning “to be kind or yield to another.” The Lord wants to be kind to his people, and the normal channel he does so is through the Church. The Church’s authority to grant indulgences is based upon the mandate of Jesus Christ: “Whatever you bind on earth shall be bound in heaven; and whatever you loose on earth shall be loosed in heaven” (Mt 16:19).

When the Church grants an indulgence, she “looses” someone from the temporal punishments resulting from sin, and this has heavenly consequences. The Church desires to dispense this grace generously, yet not indiscriminately. She wants the faithful to be prepared for this grace, lest it overwhelm them.

Consequently, the Church prescribes spiritual practices the faithful are asked to perform, not to earn the indulgence — no one can earn grace — but to demonstrate their readiness to receive grace. These practices can include praying certain prayers and receiving the sacraments. Some practices are less demanding. These demonstrate a person is partially ready to be loosed and thus can receive a partial indulgence. In extraordinary circumstances, however, the Church grants a plenary indulgence, meaning the recipient will be loosed from all (the plenitude of) temporal consequences due to sin. The Holy See has determined that the coronavirus crisis is one such extraordinary circumstance.