Yams and sweet potatoes are both root vegetables, but they are two distinct species. Yams (Dioscorea spp.) are native to Africa and Asia, while sweet potatoes (Ipomoea batatas) originated in Central America. Yams have a rough, scaly skin and come in a variety of shapes and sizes. The flesh is typically white or yellowish, but can also be purple or pink. Yams have a higher starch content than sweet potatoes, making them drier and less sweet when cooked. Sweet potatoes have a smoother skin and come in shades of orange, yellow, white or purple. The flesh is usually soft and sweet when cooked. Sweet potatoes are higher in sugar content than yams, making them sweeter when cooked. They also contain more vitamins and minerals than yams.