We humans, including Christians, are made vulnerable when we sin. Most of our sins are venial that must be cleansed not only in our mind also in our soul. That is why our Lord instituted the sacrament of penance so we
can receive absolution.
The Sacrament of Penance is where the sins that we committed after Baptism are forgiven through absolution. This is where our Sanctifying Grace was restored after baptism.
Only the Priest can administer this sacrament and give absolution to those who confess their sins.
In Matthew 16:19, our Lord Jesus Christ promised to give St. Peter the Apostle the power to forgive sins: “And whatever thou shalt bind on earth shall be bound in heaven, and whatever thou shalt loose on earth shall be loosed in heaven.”. Then in Matthew 18:18, he made the same promise to the other apostles. In John 20:21-23, after the resurrection of our Lord, He appeared to His Apostles and breathed upon them and said to them: “Receive the Holy Ghost; whose sins you shall forgive they are forgiven them; and whose sins you shall retain, they are retained.” This promise is not only for the apostles, but also for the next generation of priests under the Catholic Church, the only church that our Lord Jesus Christ builds upon St. Peter.
The sins that have been forgiven or cleansed during the Sacrament of Baptism is the Original Sins that Adam and Even made. While in the Sacrament of Penance, the sins that have been given absolution is the that we made that offend our Lord.
The Seal of Confession is where the Priest cannot tell anyone someone’s confession. They are bound to secrecy. Some people, including those in Government don’t like this Seal of Confession. For example, someone steals a money from the bank or killed another person; confess to the priest, the priest is not allowed to tell it to anyone including the police. BUT, he must encourage this person to surrender as an act of contrition.
The priest always reminds us to take this sacrament at least once a year. But when we made sins everytime, even if it is a venial, we must confess it to the Priest including before receiving the Holy Eucharist because we cannot receive our Lord if we are not in the state of grace.
“Confession is the soul’s bath. You must go at least once a week. I do not want souls to stay away from confession more than a week. Even a clean and unoccupied room gathers dust; return after a week and you will see that it needs dusting again!” -St. Padre Pio
Source: http://www.sspxridgefield.com/sacraments,