Sweet potatoes are often called yams; however, the two are actually different vegetables. The yam is a starchy, edible root that originates in West Africa and Asia. Sweet potatoes have origins in tropical America. True yams are imported in the U.S. on a very limited basis from the Caribbean. However, over the years, the produce and grocery industries have used the word 'yam' to describe sweet potatoes with vivid orange color and sweet, moist flesh. The U.S. Department of Agriculture requires that all sweet potatoes labeled as 'yams' must also carry a 'sweet potato' label.