Indulgences are a forgiveness of the temporal consequenses of sin which remain even after we have been forgiven of them. Please note the following points which are often misunderstood.
1: Indulgences do not work apart from the Grace Christ won for us on the Cross.
2: Indulgences cannot be applied to future sins because they can only be applied to those sins for which we have already repented and received absolution.
3: Indulgences cannot be “bought” but are a result of doing good works, including alms giving.