We recognize that the Sacraments have a visible and invisible reality, a reality open to all the human senses but grasped in its God-given depths with the eyes of faith.
When parents hug their children, for example, the visible reality we see is the hug. The invisible reality the hug conveys is love. We cannot "see" the love the hug expresses, though sometimes we can see its nurturing effect in the child.
During the sacrament of Penance, one confesses their sins to God through a priest who forgives their sins by God’s mercy, and orders them to live a more faithful life through absolution.