This is a Roman Catholic teaching whereby a reduction is achieved in purgatory – a place of purification before reaching heaven. An indulgence is partial if it removes part of the temporal (earthly) punishment due to sin, or plenary if it removes all punishment.
Going to confession, receiving Holy Communion, doing good deeds, abstinence, Bible reading, self-punishment (penance), and praying all done with a contrite heart besides signing themselves with the sign of the cross while saying ‘In the name of the Father, and of the Son, and of the Holy Spirit. Amen’ are some of the ways an indulgence can be granted.
See also: penance, purgatory, Roman Catholicism.
mit') is "a way to reduce the amount of punishment one has to undergo for sins". ... By the late Middle Ages, indulgences were used to support charities for the public good including hospitals.