Absolution is a religious concept for purging someone of sin, granting them absolution. The word is used for other kinds of forgiveness too.
When you sin or make a mistake, you usually want absolution — which is like forgiveness. In many religions, if you confess your sins, you can be granted absolution: the sin is forgiven, forgotten, wiped clean. Usually, the sinning person has to do some kind of penance to atone for the sin to achieve absolution. Absolution is a serious concept: if you jaywalked, you probably won't worry about absolution. If you killed somebody, absolution is going to be more important.