It just so happens that I was on this youth site today so I'll post the explanation from there.
http://catholicyouth.freeservers.com/jubilee/defin_indulg.htm
Indulgences:
the treasures of the Catholic Church
What is an indulgence?
The word "indulgence" says it all - indulgences are a special heavenly treasure which the Church grants us to repay the debt we owe God for our sins and heal the damage done to our souls by sin.
God has allowed the Church to attach indulgences to certain actions or prayers, so that when we perform these actions or pray these prayers, we can receive the indulgence.
Although indulgences cannot be applied to the living (they have to get their own indulgences!), we can help the Souls in Purgatory to reach Heaven sooner by applying the indulgences we receive, to them, to help pay their debt to God.
Why do we need indulgences?
You may be thinking,
"But I already went to confession, and God forgave my sins! Why do I still owe a "debt" to God?"
Frank Sheed, the well-known English Catholic preacher and publisher, put the answer this way: A sin is like pounding a nail into a piece of wood. When you confess your sins, and God forgives you, it's like pulling the nail out of the wood. But the hole remains, and has to be filled in. We have hurt our souls, and now we have to fix the damage.
Because of Original Sin (Adam's and Eve's sin of disobedience in the Garden of Eve), human beings find it easier to sin than to do good. Each sin wounds our souls by making it harder for us to resist committing the same sin next time. Even after we have repented, we have to overcome this tendency by penance. The saints understood this very well; they often mortified themselves with large or small penances to keep in control of their passions.
However, since we can't see the damage sin does to our souls, we often aren't sorry enough for our sins, and we forget to pray and do penance for them. Because of this, God has to cleanse our souls, either in this life, through trials, or in the next, in Purgatory. So God, through the Church, provides us with an "incentive" to prayer and penance: indulgences. When we perform an action or say a prayer to which the Church has attached an indulgence (i.e. praying before the Blessed Sacrament, saying the Rosary, etc.), the Church uses the treasury of Jesus' merits to "pay" part or all of our debt to God and purify our souls for us, provided we have the intention of gaining the indulgence.
One of the nuns who belonged to St. Teresa of Avila's order realized the importance of indulgences, and never lost an opportunity to gain them. When she died, St. Teresa was greatly surprised to see this nun's soul rise straight to Heaven, bypassing Purgatory! Since this nun had seemed to be quite ordinary, St. Teresa asked Jesus the reason why she had gone straight to Heaven. Jesus answered that because of all the indulgences this sister had faithfully obtained, she had completely paid back her many debts to God, so that her soul was spotless at the moment of death!
The Church's Treasury of Grace
The Catholic Church is able to grant indulgences because she draws on the infinite merits of Christ, Mary, and all the saints. Blessed Mary of Quito, a Spanish nun, saw in a vision a vast treasure, which, God explained to her, symbolized the graces and merits of Jesus (the treasure of the Church!) from which indulgences are taken. These graces and merits can be obtained by anyone who fulfills the conditions, usually quite easy, for receiving an indulgence. People who don't bother to take advantage of indulgences are like travellers passing through a field full of precious jewels, who don't even take the trouble to bend over and fill their pockets, even though they know they will need these treasures when they reach their destination.
The Church was given the authority to grant indulgences by Jesus, when He gave St. Peter the keys to the kingdom of Heaven.
"I will give you the keys of the kingdom of heaven, and whatever you bind on earth shall be bound in heaven, and whatever you loose on earth shall be loosed in heaven." (Matthew 16:19) In modern-day language, Jesus might have said, "I am giving you the P.I.N. to my heavenly bank account."
In the fifteenth and sixteenth centuries, the Church granted indulgences for giving alms to help build the beautiful cathedrals which were being erected at the time. This unfortunately led to the wrong idea that the Church was selling the indulgences to make money. As a result, the Protestant reformers of the time completely rejected the doctrine of indulgences as an abuse of the Church's power. They were mistaken; even though some abuses did occur, the Church's power to grant indulgences comes from God. However, they were right in that you can't simply buy indulgences like "quick-fix" medicines for your soul! You have to have the proper spirit of sorrow for sin to benefit from the indulgence.
Kinds of Indulgences
There are two kinds of indulgences: partial indulgences, and plenary indulgences.
Plenary indulgences: The word "plenary" means "full," so a plenary indulgence takes away
all the punishment due to our sins. If someone received a plenary indulgence, and died immediately afterwards, that person would not even have to go to Purgatory! Wow! So how can that happen? The answer is simple: the grace available in an indulgence is infinite (it comes from the merits of Christ, remember?), but our own sorrow for our sins is a large factor in receiving these graces. One of the conditions for gaining a plenary indulgence is that you have to have
no attachment to sin. You have to be perfectly sorry for your sins, and never want to commit them again. This true repentance opens your soul wide to God's grace, so you can receive the full effect of the indulgence. However, if you perform an action or prayer which is attached to a plenary indulgence, but you are still attached in some way to your sins, you receive a partial indulgence.
Partial indulgences: A partial indulgence takes away part of the punishment due to our sins. The Church attaches a partial indulgence to less important prayers and actions. A long time ago, indulgences used to be measured in "days" or "years," which were equivalent to an equal length of time spent doing severe penance (i.e. if you said a certain prayer, you could get an indulgence of "forty years.") However, this led to people simply adding up the days and years of indulgence they had gained instead of concentrating on true sorrow for sin, so the Church abolished these indulgences in 1969 in favour of the term "partial indulgence." A partial indulgence is not measured in definite time lengths, because its efficacy depends on our own openness to God and our rejection of sin. Even partial indulgences are very valuable to us - would you complain if you owed a debt of $20,000, and someone paid $6,000 for you?!
Note: A partial indulgence may be gained several times a day. A plenary indulgence can only be gained once a day.
Conditions for gaining a plenary indulgence
1. Perform the action or say the prayer to which the indulgence is attached
2. Confess your sins with true sorrow for having offended God.
3. Receive Holy Communion
4. Pray for the intentions of the Holy Father (the usual prayers are an Our Father, Hail Mary, and Apostles' Creed)
Note that Communion should be received for each plenary indulgence, but one Confession can be used for several indulgences.
Some Indulgenced Prayers and Actions
General Grants
- "A partial indulgence is granted to the faithful who, in the performance of their duties and in bearing the trials of life, raise their mind with humble confidence to God, adding - even if only mentally - some pious invocation." (i.e. "Holy Mary, pray for us", etc.)
- "A partial indulgence is granted to the faithful, who, in a spirit of faith and mercy give of themselves or of their goods to serve their brothers in need."
- "A partial indulgence is granted to the faithful, who in a spirit of penance voluntarily deprive themselves of what is licit and pleasing to them."
- A partial indulgence is granted to the faithful who witness to their faith in a non-Catholic environment (this can even be something so simple as saying grace in a restaurant!)
Various indulgenced prayers
- Rosary, (plenary indulgence if recited in church, or with a group or family; partial indulgence in other circumstances)
- Stations of the Cross, Nicene Creed, (plenary)
- Litany of the Sacred Heart of Jesus, the Litany of the Blessed Virgin Mary, or the Litany of All Saints (partial)
- "Hail Holy Queen," "Apostles' Creed," Sign of the Cross, Prayer for vocations to the religious life and the priesthood(partial)
Various indulgenced actions
- A visit to a cemetery with prayer for the dead (plenary from 1st to 8th November, partial all other days. This indulgence is given to the Souls in Purgatory).
- A visit to adore the Blessed Sacrament (partial; plenary for a visit lasting more than half an hour)
- Reading the Holy Bible (partial; plenary for over half an hour)
- Teaching or learning Christian doctrine (partial)
- Spending at least three days in a retreat (plenary)
- Participating in the Adoration of the Cross during the Good Friday liturgy, and devoutly kissing the cross (plenary)
- Renewal of one's baptismal promises (partial; plenary if the renewal is made on the Vigil of Easter or on the anniversary of one's baptism)
Note: there are many other indulgences available: consult the
Enchiridion of Indulgences, available from any Catholic bookstore, for a complete list.
<A href="http://catholicyouth.freeservers.com/jpII_messages/indulgence.htm">
Read what the Holy Father says about indulgences
DID YOU KNOW??
Although you can't apply the indulgence to a living person (they have to get their own indulgences!) you can ask God to apply your indulgence to relieve the
Holy Souls in Purgatory. And don't forget to ask the Holy Souls to pray for you when they get to Heaven; you'll be gaining friends in high places!