In visions, saints (like those who received the stigmata, for example) who were spoken to by Jesus and/or the Virgin Mary have spoken of this. The holy mother did not want her story to compete with that of her Son, so did not want it written or shared until much later. She gave people the rosary to help focus their meditation on the mysteries of the life of her Son, look it up. It is a weapon against evil, and a help on the way to get closer to her Son which is the only way to get to God.