Caribbean White Soft Yam

Yams are often mistakenly called sweet potatoes and vice versa, but these are actually two different vegetables. A true yam is the tuber of a tropical vine and it's not even distantly related to the sweet potato. Yams are a popular vegetable in Africa Latin American and the Caribbean. This tuber can grow over seven feet in length. 

The yam's botanical name is dioscorea batatas.
Depending on country and region, it may also be called a boniato, njam, nyami, djambi, yamswurzel, ñame or igname de chine.
How to Identify a Real Yam 
True yams are indigenous to Africa and Asia with most being grown in Africa, but there are over 150 varieties of yams available worldwide. True yams have rough, dark skin. Their flesh can range from white to a reddish color, and yellow but it's usually white. 
Although you might find canned vegetables labeled as yams, these probably aren't true yams. Even the "yams" found in fresh produce sections of grocery stores are rarely real yams. They're soft sweet potatoes, which are different from firm sweet potatoes.
Africa, the native land of the yam, grows 95 percent of more than 600 varieties of the crop. Yams favor tropical and sub-tropical weather during their growing season and do not tolerate freezing.