309. Is a confessor bound to secrecy?Given the delicacy and greatness of this ministry and the respect due to people every confessor, without any exception and under very severe penalties, is bound to maintain "the sacramental seal" which means absolute secrecy about the sins revealed to him in confession.
Further reading: CCC 1467310. What are the effects of this sacrament?
The effects of the sacrament of Penance are: reconciliation with God and therefore the forgiveness of sins; reconciliation with the Church; recovery, if it has been lost, of the state of grace; remission of the eternal punishment merited by mortal sins, and remission, at least in part, of the temporal punishment which is the consequence of sin; peace, serenity of conscience and spiritual consolation; and an increase of spiritual strength for the struggle of Christian living.
Further reading: CCC 1468-1470 , 1496