All, especially children, should know this act well before going to confession.
231 Q. What is an indulgence? A. An indulgence is the remission in whole or in part of the temporal punishment due to sin.
I have explained before what the temporal punishment is; namely, the debt which we owe to God after He has forgiven our sins, and which we must pay in order that satisfaction be made. It is, as I said, the value of the watch we must return after we have been pardoned for the act of stealing. I said this punishment must be blotted out by our penance. Now, the Church gives us an easy means of so doing, by granting us indulgences. She helps us by giving us a share in the merits of the Blessed Virgin and of the saints. All this we have explained when speaking in the Creed of the communion of saints.
232 Q. Is an indulgence a pardon of sin, or a license to commit sin? A. An indulgence is not a pardon of sin, nor a license to commit sin, and one who is in a state of mortal sin cannot gain an indulgence.
If you are in a state of mortal sin you lose the merit of any good works you perform. God promises to reward us for good works, and if we are in the state of grace when we do the good works, God will keep His promise and give us the reward; but if we are in mortal sin, we have no right or claim to any reward for good works, because we are enemies of God. For this reason alone we should never remain even for a short time in mortal sin, since it is important for us to have all the merit we can. Even when we will not repent and return to Him, God rewards us for good works done by giving us some temporal blessings or benefits here upon earth. He never allows any good work to go unrewarded any more than He allows an evil deed to go unpunished. Although God is so good to us we nevertheless lose very much by being in a state of mortal sin; for God’s grace is in some respects like the money in a bank: the more grace we receive and the better we use it, the more He will bestow upon us. When you deposit money in a savings bank, you get interest for it; and when you leave the interest also in the bank, it is added to your capital, and thus you get interest for the interest. So God not only gives us grace to do good, but also grace for doing the good, or, in other words, He gives us grace for using His grace.
233 Q. How many kinds of indulgences are there? A. There are two kinds of indulgences—plenary and partial.
234 Q. What is a plenary indulgence? A. A plenary indulgence is the full remission of the temporal punishment due to sin.