In the Catholic belief there are two types of punishment for sins: eternal and temporal. The Sacrament of Penance basically “washed” away eternal punishment, but the temporal punishment remains. The thing that “washed” away temporal punishment is something known as an indulgence. But what is an indulgence exactly?
An indulgence is a way to reduce or eliminate temporal punishment to put it plainly. A common misconception about indulgences is the fact that it is the act of buying the forgiveness of sins from church, this is not correct in a lot of cases. Also indulgences in general do not necessarily involve monetary donation to the church, but that does not mean it is right. Indulgences were actually given out by the church when people confessed their temporal sins.
If someone did not confess their temporal sins and receives an indulgence, that indulgence is invalid. When a person does not confess their temporal sins before death the soul of that person would enter a place known as Purgatory: not hell nor heaven because temporal sins were not eternal sins and were seen as not as punishable as eternal sins in the Catholic church. In Purgatory that person will undergo a purification process, to be able to enter Heaven.
In conclusion, in the Catholic belief there are two types of punishment for sins: eternal and temporal. The way to wash away temporal sin is with something called an indulgence. An indulgence reduces or eliminates the temporal punishment of temporal sin, only this happens when a person confesses first. Today there are definitely misconceptions on indulgences, including the belief that it was the act of buying the forgiveness of sins, which is incorrect in a lot of cases. But again even debunking the misconceptions on indulgences does not mean it was a good practice of the Church.