The Church invites and encourages the faithful to honor the saints by venerating their relics and images. They have always been a significant part of the life of the Church. Since the fourth century, relics were deposited in the altars of the Church during their dedication.
Veneration is the honor we give to the saints, especially the Blessed Virgin Mary. Contrary to what other Christians and non-Christians believe, when we venerate the saints, we do not worship them. There is an essential difference between the divine worship (latria) owed to God and the veneration (dulia) paid to the saints. The honor given to the relics of saints and to their images does not detract from the worship given to God. By honoring the saints, their relics and images, one honors God from whom comes all holiness.
The Council of Trent (1563) defended the Christian practice of invoking the prayers of the saints and venerating their relics and burial places. The Church, however, absolutely forbids the selling of sacred relics which are generally accompanied by proper documentation attesting to its authenticity.
There are three classes of relics. A first-class relic is a part of the saint’s body (this is the part inserted in the altar). A second-class relic is a piece of the saint’s clothing or something used by the saint. A third-class relic is an object which has been touched to a first-class relic. So if your rosary, medal, or holy card has touched a first-class relic, you now have custody of a third-class relic!