Indulgences are not 'tickets to Heaven'. Besides, we cannot purchase Heaven with all the money and good works in the world. Jesus Christ's death on the Cross is the only ticket we will ever need to enter Heaven.
Granted, there was a time when some individuals misused indulgences to collect money. Their errors were soundly condemned by the Council of Trent. You cannot condemn the entire Church for their action any more than you can condemn all Televangelists for the actions of a few.
So, what is an indulgence? It is the removal of the temporial effects of sin. What does that mean in English? Simply, it means that every sin has effects that go beyond what is forgiven. A child who breaks a vase playing ball in the house my be forgiven by his parents but the temporial effects (the broken vase) still exist and must be atoned for (repaired). This is what an indulgence does.
Catholic Answers
Catholic Answers has a more detailed explanation (including Scripture references) on their site. I encourage anyone with questions about the Catholic Faith to visit their site and submit a question.
