Cruise the potato section in most produce stores and you´ll likely see a sign for yams above coppery-colored, pointy root vegetables. Visit an Asian or Hispanic market and you'll find a decidedly different vegetable—with dark, rough, scaly skin—also labeled as a yam.
The truth is that the supermarket yam is not a yam at all, but a type of sweet potato.
The sweet potato is grown around the world, although it's indigenous to the Americas and is especially popular in the southern United States. According to the North Carolina Sweet Potato Commission, the naming confusion began decades ago when Louisiana farmers developed a new sweet potato with dark-orange flesh that´s moister than the light-skinned, pale-fleshed sweet potatoes. To distinguish this new breed, they called it a yam and the name stuck. Today, the USDA requires that these "yams" (sometimes called American or Louisiana yams) also be correctly labeled as sweet potatoes.
The true yam is an unrelated species that's much starchier than the sweet potato and is a staple food for much of Latin America, Africa, and Asia. Called ñame or igname, it can be huge and irregularly shaped. The skin is usually pale to dark brown, and the crisp, dry flesh is white to ivory to yellow. Yams taste rather bland and they aren´t sweet.