Why do Catholics confess their sins to the priest? - Joe Non-Catholic

Dear Joe:

What an important question!  Let's begin with an understanding of what happens when a person sins:  Every sin damages our relationship with God.  However, every sin also damages to some degree, our relationship with the people of God ie: the Church.  When we sin we violate that which the people of God (The Church) hold as Truth.  And, "to some degree, ... our communion with our brothers and sisters in Christ is weakened, -or even broken."
     And, our sin also "damages our relationship with humanity.  Sinning hurts our fellow human beings" and even ourselves.  
     "If we're to apologize and attempt to change our behavior, who deserves to receive that apology?  We owe an apology to God, everyone in the Church, and every human being.  These are the relationships that need to be healed. Yet this would be next to impossible."  How could we apologize to every person in the Church and every person in the world?  
     "This is where the priest comes in.  A priest is unique.  He's a mediator between God and people.  By his ordination, he is God's representative or ambassador on earth.  The Church gives him the power to speak on its behalf, and he represents humanity before God.   In a special way, a priest has the faculty to speak on behalf of all the parties who deserve an apology.  So the priest receives our confession on behalf of God, the Church, and all of humanity.
     "But the priest goes beyond accepting the apology.  He helps us fulfill the requirement of contrition.   Contrition exceeds and apology.  It's a desire not to repeat the offense. This may be difficult, so we always ask for God's grace to avoid sin.  But even hearts that [don't] want to sin need help knowing how to avoid it."
    When we go to the priest and say we are sorry, we are acknowledging that we must apologize to God and to all our brothers and sisters in Christ whom we have let down by our sin.  Because of his ordination, he is the person who can speak for Christ and forgive us and he is the representative of all the people of the Church and he can accept the apology.   - We get a two-fer!  It's the same idea we have in our government.  We have Representatives who made decisions for the people of the United States because we elect that person to speak for us.  The priest is the one who can speak for Christ during the Sacraments.  And, as a priest, he is the Representative of us, the people of the Church.  
     So, we say we are sorry and then the priest gives us something to think about and tells us what we should do to make things right - or to reconcile ourselves with God and the Church and humanity.  He gives us a penance.  "Penance is like medicine for the soul.   If we understand the purpose of the penance, we begin a practice that can help us avoid a particular sin.  ... the idea is that we've at least started on the right path to avoid sin, and now we may freely choose to continue on that path."  Through the priest who acts as the person of Christ for us, our sins are forgiven. In other words, "Jesus forgives our sins through the priest and doesn't hold us guilty."
     "Jesus' forgiveness allows established relationships to be restored and new relationships to begin - even though the effects of the sinful action may still exist in the real world."  
("Medicine for the Soul"  by Fr. Donald Willard, CSsR , Liguorian Magazine, April 2014   p 5.)