Sweet potatoes are prevalent in the Americas and come in a number of varieties of substance and sweetness. These are typically the orange colored ones, though you might see them in purple and other colors.
Yams, on the side of the tubular continuum, are common in Africa and are more fibrous and whiter on the inside than a sweet potato. In fact, you likely have never seen a Yam.
Bonus Tip: Best Scalloped Sweet Potato Dish: 3 easy ingredients. You got this.