Nearly all of the sweet potatoes found in the US fall into two categories: (1) golden skin with creamy white flesh, and (2) brown or copper skin with an orange flesh. Orange sweet potatoes have a sweet, smooth, soft texture. White sweet potatoes, on the other hand, have a milder flavor and crumblier, more potato-like texture when cooked.  FYI: True yams are almost impossible to find in the States. Those things you grew up calling 'yams' were almost certainly orange sweet potatoes.