Confession is considered a holy Sacrament in the Coptic Orthodox Church. Confession means to the Orthodox faithful, verbal confession before a Confession Father of sins and mistakes done by the person who is confessing and humbly repenting. This sets forth the absolution and forgiveness of sins. When the Lord Jesus Christ instituted the Sacrament of Repentance and Confession, He said, "Assuredly, I say to, whatever you bind on earth will be bound in Heaven, and whatever you loose on earth, will be loosed in Heaven." (Matthew 18:18). Please also read (Matthew 16:19).
Following the Holy Resurrection, the Lord Jesus Christ said, "As the Father sent Me, I also send you." And when He said this He breathed on them, and said to them: "Receive the Holy Spirit. If you forgive the sins of any, they are forgiven them, if you retain the sins of any they are retained." (John 20:21-23)

By saying this, the Lord Jesus Christ gave them the authority of binding sins or loosing them, and the authority of the Holy Spirit given to them according to conditions and repentance of the confessing person. The confession was practiced in the Old Testament (Lev 5:5,6), (Matt 3:6) and the apostles themselves used this authority (Acts 19:18), (1Cor 5:5), (2Cor 2:6,7), (1Tim 5:20), and (James 5:16). Also an important point to note, the priest actually doesn't absolve the person confessing, but says, "May God absolve you," as he does not absolve alone but obtains the absolution from God, the origin of absolution and forgiveness. We should practice confession before communion as our teacher St. Paul taught us in 1Cor 11:27-29.

There is a very good book to read, "Repentance and Confession" Sacrament 3 written by His Grace Bishop Mettaous. Also if you will search the Question and Answers link of this website under Spiritual Life, you will note that questions 1,8,17, and 25 refer to different aspects of the Sacrament of Confession.