Wal-Mart Stores, Inc. is the world's largest retailer by revenue, with $482.1 billion in sales for 2016, primarily from its U.S. operations. The company operates in three main segments: Walmart U.S., Walmart International, and Sam's Club, and heavily relies on the U.S. market for its revenue. Challenges include increasing saturation in foreign markets and overdependence on U.S. sales.