As a former Roman Catholic, but now drifiting towards Anglicanism, I would like to clarify the Catholic Church's teaching on confession:
The Church believes that God has already forgiven you for your sins when Jesus died on the cross. Confession is not about the Priest forgiving you, but Jesus saying through the Priest, you are forgiven, and you accepting that forgiveness in your heart. The Priest acts as Jesus' stand in/representative. Catholic/Greek Orthodox/Jewish/Ancient Near Eastern theology believes that you don't have direct access to God: God mediates the experience of itself to you through some form of material reality.
These signs/symbols are called sacraments, and theyre basically a physical material thing that acts as a conduit to the deeper spiritual reality that is God. In Confession, since Jesus is believed to be God, Jesus acts through the Priest, who becomes the sacrament/symbol/sign representing Jesus.
What it basically boils down to is God uses people/material things (such as the bread and wine in communion or the water in baptism) to reveal itself to us and communicate to us through them in a way that we can comprehend as finite beings, as I think the implication is is that if we had direct access to God, who is believed to be an infinite, timeless, spaceless, being who is both outside of time and yet is present at every point in time, our heads would explode from the sheer overwhelmingness of the experience. Basically, God doesn't want our brains to explode from mental overload, so it presents itself through signs and symbols in a way we can understand. This includes people such as a Priest.
Hope that helps.