Beads for counting prayers are common in many religions. In Christianity, the Orthodox Church has Jesus beads.
In Catholicism, there are different kinds of chaplets, such as Divine Mercy, Infant of Prague, Saint Michael the Archangel, and of course the rosary. The rosary is a sacramental and should be blessed by a priest or deacon. Once blessed, it is set apart for spiritual use.
Saint Dominic is attributed as the one who received the first rosary. He did so by way of an apparition of our Blessed Mother. Mary gave him the rosary as a spiritual tool to fight the heresy of Albigensianism, which denied the humanity of Christ. His preaching was not able to fight the errors prevalent in the thirteenth century, but the simple rosary, whereby the believer meditated on the Joyful, Sorrowful, and Glorious Mysteries of Jesus Christ, helped convince the people of Spain and France that Jesus was truly God and Man, human and divine.
The Sorrowful Mysteries especially underscore the human nature, since Jesus felt real pain and died a real death which only a human could experience. The Glorious accentuate the divine nature since only divinity can rise from the dead and ascend into heaven. The Joyful bridge the gap of heaven and earth, divine and human in that Jesus had a real human mother in Mary but she conceived miraculously by divine power of the Holy Spirit.
The rosary consists of twenty mysteries which center on the life of Christ. These mysteries were taught to people who could not read and write, and soon they began to learn their faith. A famous painting that is enshrined in a church in Pompeii is said to be the miraculous depiction of Our Lady of the Rosary. In the painting our Lady is giving the rosary to Saint Dominic and Saint Catherine of Sienna. Saint Catherine is cofounder, along with Saint Dominic, of the Dominican Sisters.
The twenty mysteries of the rosary are divided into four categories. First are the joyful mysteries, which include the Annunciation, Visitation, Nativity, Presentation, and Finding in the Temple. The second category centers on the passion of Christ, known as the sorrowful mysteries, which include the Agony in the Garden, the Scourging at the Pillar, the Crowning of Thorns, the Carrying of the Cross, and the Crucifixion. Third, the glorious mysteries comprise of the Resurrection, Ascension, and Descent of the Holy Spirit, Assumption of Mary, and Coronation of Mary. Pope John Paul II dedicated the year 2003 to the rosary and composed the last five mysteries of light, known as the Luminous Mysteries, which consist of the Baptism of the Lord, Wedding Feast of Cana, the Preaching of the Kingdom, the Transfiguration, and Institution of the Holy Eucharist.
The contemporary rosary is comprised of fifty beads, and for each bead a prayer is said. It begins on the crucifix with the Apostles Creed followed by one Our Father, three Hail Marys, and one Glory Be to the Father. Then the first mystery is announced followed by one Our Father, ten Hail Marys, and one Glory Be to the Father. This is repeated five times and concludes with the Hail Holy Queen. The rosary can be repetitious if it is not prayed in the proper spirit. When one meditates on each of the mysteries, the Hail Marys become the background for one to meditate on a certain scene.
Every pope in the last 400 years has written some point on the power of this spiritual tool. It is a great preparatory or thanksgiving tool for Mass. When said in public in front of the Exposed Blessed Sacrament, the Church grants a plenary indulgence, provided the person follows the norms for this spiritual instrument.