From the LCMS website:
Esther is the heroine of the biblical book that bears her name. Her Jewish name was Hadassah, which means “myrtle.” Her beauty, charm, and courage served her well as queen to King Ahasuerus. In that role she was able to save her people from the mass extermination that Haman, the king’s chief advisor, had planned (2:19–4:17). Esther’s efforts to uncover the plot resulted in the hanging of Haman on the very same gallows that he had built for Mordecai, her uncle and guardian. Then the king named Mordecai minister of state in Haman’s place. This story is an example of how God intervenes on behalf of his people to deliver them from evil, as here through Esther he preserved the Old Testament people through whom the Messiah would come.