Our Holy Father, Pope John Paul II, has asked "for renewed pastoral courage in ensuring that the day-to-day teaching of Christian communities persuasively and effectively presents the practice of the Sacrament of Reconciliation" (Novo Millennio Ineunte, 37). A renewed appreciation for this wonderful sacrament which leads many to return to the life of grace will bring about a new springtime, a new era of growth and life for the Church. We invite every Catholic to celebrate the sacrament of Penance or Reconciliation or, as we have traditionally said, "go to Confession," on a regular basis. There can be no better way to make progress on our spiritual journey than by returning in humble repentance and love to God, whose forgiveness reestablishes us as his children and restores us to peace with his Church and our neighbors.

The Catechism of the Catholic Church tells us that “there is not a single aspect of the Christian message that is not in part an answer to the question of evil” Sin is another name for the evil of human failure and iniquity. The “good news” is that sin has been overcome by the Passion, Death, and Resurrection of the Incarnate Word, Jesus Christ. Yet sin still persists in the word, even in the lives of the faithful. The Sacrament of Penance and Reconciliation is a great gift to the Church. It is a privileged means for experiencing the mercy of God. This sacrament enables us to undergo purification and detachment from sin, which is necessary for authentic growth in holiness. 

Reconciliation between God and his people was brought about by our Lord Jesus Christ in the mystery of his death and resurrection (see Romans 5:10). The Lord entrusted the ministry of reconciliation to the Church in the person of the apostles (see 2 Corinthians 5:18). The Church carries out this ministry by bringing the good news of salvation to people and by baptizing them in water and the Holy Spirit (see Matthew 28:19). 

Because of human weakness, however, Christians “leave [their] first love” (see Revelation 2:4) and even break off their fellowship with God by sinning. The Lord therefore instituted a special sacrament of penance for the pardon of sins committed after baptism (see John 20:21-23) and the Church has faithfully celebrated the sacrament throughout the centuries—in varying ways, but retaining its essential elements.

The Church is deeply concerned with calling the faithful to continual conversion and renewal. It desires that the baptized who have sinned should acknowledge their sins against God and their neighbor and have heartfelt repentance for them; it takes pains to prepare them to celebrate the sacrament of penance. For this reason the Church urges the faithful to attend penitential celebrations from time to time.  

A serious, grave or mortal sin is the knowing and willful violation of God's law in a serious matter, for example, idolatry, adultery, murder, slander. These are all things gravely contrary to the love we owe God and, because of Him, our neighbor. As Jesus taught, when condemning even looking at a woman lustfully, sin can be both interior (choices of the will alone) or exterior (choices of the will carried into action). A man who willfully desires to fornicate, steal, murder or some other grave sin, has already seriously offended God by choosing interiorly what God has prohibited.

Mortal sin is called mortal because it is the "spiritual" death of the soul (separation from God). If we die without repenting we will lose Him for eternity. However, by turning our hearts back to Him and receiving the Sacrament of Penance we are restored to His friendship. Catholics are not allowed to receive Communion if they have unconfessed mortal sins.

Venial sins are slight sins. They do not break our friendship with God, although they injure it. They involve disobedience of the law of God in slight (venial) matters. If we gossip and destroy a person's reputation it would be a mortal sin. However, normally gossip is about trivial matters and only venially sinful. Additionally, something that is otherwise a mortal sin (e.g. slander) may be in a particular case only a venial sin. The person may have acted without reflection or under force of habit. Thus, not fully intending the action their guilt before God is reduced. It is always good to remember, especially those who are trying to be faithful but sometimes fall, that for mortal sin it must not only be 1) serious matter, but 2) the person must know it is serious and then 3) freely commit it. 

These two categories of sin are explicitly to be found in Sacred Scripture. In the Old Covenant there were sins that merited the death penalty and sins that could be expiated by an offering. This Law was a teacher that prepared the way for the faith (Gal. 3:24). In the New Covenant these material categories are replaced by spiritual ones, natural death by eternal death. There are thus daily faults for which we must daily ask forgiveness (Mt. 6:12), for even the "just man falls seven times a day" (Prov. 24:16), and mortal faults that separate the sinner from God (1 Cor. 6:9-10) for all eternity.