Through Reconciliation, Christians are freed from sins committed after Baptism. The Sacrament of Reconciliation is considered the normal way to be absolved from grave or mortal sins.
The Sacrament has four elements, three on the part of the penitent (contrition, confession and satisfaction) and one on the part of the minister of the Sacrament (absolution).
Catholics distinguish between two types of sin: Mortal and Venial.
Mortal sins are a grave violation of God's law that turns us away from God. For a sin to be a mortal sin, three conditions must be present: grave or serious matter, full knowledge of the evil of the act, and full consent of the will (i.e., free and deliberate consent).
Venial sins are the kind that "do not set us in direct opposition to the will and friendship of God", can be remitted by contrition and reception of other Sacraments, but they too are rightly and usefully declared in confession.