During the festival of Passover, Jews recount the story of the Exodus, when Jews escaped from slavery in Egypt.  These books, called haggadot, were used in Passover celebrations.  Jews traditionally gather for dinner and, following a prescribed order (or seder), eat certain foods such as unleavened bread, known as matzah, or bitter herbs, known as maror, in order to remind themselves of the hardships of slavery.  Over the centuries, Passover celebrations were often the source of anti-Semitic outbreaks among non-Jews, who believed falsely that Jewish customs required the murder of Christian children.