The Rosary is a Scripture-based prayer. It begins with the Apostles' Creed, which summarizes the great mysteries of the Catholic faith. The Our Father, which introduces each mystery, is from the Gospels. The first part of the Hail Mary is the angel's words announcing Christ's birth and Elizabeth's greeting to Mary. St. Pius V officially added the second part of the Hail Mary. The Mysteries of the Rosary center on the events of Christ's life. There are four sets of Mysteries: Joyful, Sorrowful, Glorious and––added by Saint John Paul II in 2002––the Luminous.   

--excerpt from the United States Conference of Catholic Bishops (USCCB) website