So yams and sweet potatoes are quite different. Yams have rough, dark brown skin that is similar look and feel to tree bark, and the flesh is dry and starchy like a regular potato. Sweet potatoes have smooth reddish skin, softer flesh (when cooked), and a sweet flavor. Fortunately, you are unlikely to find true yams at the US grocery stores, they are mostly varieties of sweet potatoes. The way to tell them apart is by the outer look: yams (besides being much darker and rougher) develop eyes or buds just like a regular potato, but a sweet potato does not. Sweet potatoes may have fine roots at one end, just like beets or carrots. Do NOT use canned!