I'm preaching a retreat in Idaho and ran across this devotional shrine of Our Lady of Lourdes.
In 1858, the Blessed Mother of Jesus, appeared to the French shepherd girl, St. Bernadette Soubirous, to ask the world to pray for the conversion of sinners. This is typical of Mary's mission to draw attention to her Son and to bring souls to Him.
Although these apparitions have been approved by the Roman Catholic Church, they are not an article of faith. In other words, Catholics may believe in the apparitions, but are not bound to.