In most national US markets, so-called yams are often sweet potatoes. True yams, which are commonly grown in parts of Africa, are a totally different vegetable. While they resemble sweet potatoes and can be used interchangeably, yams are thicker skinned and more pale, and have more starchy flesh. The confusion dates back to the when enslaved Africans referred to native American sweet potatoes as nyami, a West African word for yam. The term stuck and most people do not usually know what they are actually buying.
There are thousands of varieties of sweet potatoes. They come in different sizes and color, both outside and inside and are mostly grown in the southern United States. I like the darker flesh and skinned sweet potatoes often found in 3 pound bags. Sweet potatoes in my opinion have a sweeter, lighter taste than yams. They can be used interchangeably but next time you are in the market, check and see where they are from or if they are actually a sweet potato or a yam.
Try sweet potatoes in these delicious dishes: