Sweet Potato vs. Yam

Member of the morning glory family; comes in orange, white, or purple flesh.

Belongs to the yam family; native to Africa and Asia; much drier and starchier.

Sweet Potato
Skin: Smooth, thin skin (orange, tan, or purple).
Flesh: Orange, white, or purple flesh 
Shape: Tapered ends

Yam
Skin: Rough, scaly bark-like skin.
Flesh: White, purple, or reddish flesh.
Shape: Cylindrical, often long and thick. 

Sweet Potato: Sweeter, moist, soft when cooked.

Yam: Mild, starchy, and dry; more like a regular potato in flavor.

Sweet Potatoes: Common in U.S. grocery stores.

Yams: Rare in the U.S.; mostly found in international or African markets.

In the U.S., orange-fleshed sweet potatoes are often labeled “yams”—especially in the South—to distinguish them from the white-fleshed variety. But these are not true yams.