A yam is a starchy vegetable that grows underground. Yams are similar to potatoes — they can be baked, boiled, mashed, grated, or cut into chunks.
In North America, a yam is the same thing as a sweet potato, although in most parts of the world these words refer to two completely different vegetables. Yams have flesh that ranges in color from white to deep orange and tastes slightly sweet. The word yam started as igname, from the Portuguese inhame, from a West African source.