A great many things. Primarily Ruth was a Moabitess, a descendant of the Moabites, who was marrying into the lineage which God was developing as the ancestors of King David and, ultimately, therefore the ancestors of Jesus Christ. It's significant that, after bringing the Moabite bloodline into the sacred Bloodline, God wiped out the rest of the Moabites. David had just enough of that bloodline of Giants to discern who among captured Moabites was carrying the Giant gene, and he decapitated those. The Giants were descendants of Nefilim, offspring of Angels and Earth women (Genesis chapter 6). Also significant was the widowed Ruth "cleaving unto" her mother-in-law and, gleaning for her in the field of Boaz, becoming the bride of Boaz an important Hebrew and key ancestor of the Judahite Royal Family. Ruth was a princess of her people, therefore a priestess of Chemosh, an evil god that demanded infant sacrifice which she rejected, becoming a devotee of the Hebrew God.