The New York Times weighs in on the important question of whether yams and sweet potatoes are interchangeable. It explains the difference:
“Sweet potatoes are New World tubers [a member of the Morning Glory family] that were adopted by enslaved Africans on the American continent. They could be grown in the temperate climates; they could be stored in mounds and used as needed to supplement meager rations. When cooked in the ashes of a dying fire, they were a sweet treat at the end of a bone-tiring day of toil. Most important, sweet potatoes were taken to the hearts and stomachs of Africans and their descendants in the United States because they recalled the true yam of Africa.
The yam, a large hairy tuber that bears no botanical relationship to the sweet potato [a member of the lily family], grows mainly in tropical and subtropical climates and is of primary importance to many West African societies. From Ghana to Nigeria, yam festivals celebrate the desire for a bounteous harvest and the continuity of life. In languages of the West African coast, including Wolof in Senegal and Umbundu in Angola, the tuber is so popular that some variant of the word “yam” simply means “to eat.” [As an example, “something to eat” is nyami in Guinea. ]”
There are approximately 200 different varieties of yams with flesh colors varying from white to ivory to yellow to purple while their thick skin comes in white, pink or brownish-black. I, myself, prefer yams, and in fact, eat so many, that perhaps I, too, should just use the word to mean “to eat.” On the online library Innvista I found that:
“In Papua New Guinea, the people have managed their crops for thousands of years without disturbing the forest around them. The women may prepare them, but yams are strictly grown and harvested in secret by the men away from the women. At special yam festivals, prize tubers can be as long as six feet and weigh as much as 200 pounds. Reflecting the status of the grower within the community, these ceremonial yams are the focus of exchanges and given as gifts to the women at the end of the festivities”.
Many people eat yams at Thanksgiving, popularly in a casserole with marshmallows on top. I myself prefer a casserole in which yams are mixed with with butter, maple syrup, and heavy cream. You can find an easy recipe for something similar here.
By the way, I cook yams in the microwave. (Okay, I cook almost everything in the microwave.) I just pierce it a few times with a knife, wrap it in a paper towel, and cook it about 8-10 minutes, turning it over at the halfway mark. The skin then peels off easily and it’s ready to go.