Sweet potatoes vs. yam

I bought two kinds of sweet potatoes (yams) yesterday. I never knew the difference between the two names. But these two kinds of tubers are very different. One has red skin and cream yellow flesh, while the other beige-y skin and starchy deep purple flesh. They both look very different from super market sweet potatoes most of us have seen. I baked them in a 400 degree oven for 40 minutes. They look so pretty.

I knew that there were more varieties of yams out there that I have or have not encountered before. I've always just grouped them under the big umbrella of sweet potatoes or yams, even though I knew they were very different. So I went online and was determined to find out more about these tubers.
Here's an article from Chef Zoe Francois. She apparently had the same confusion and she did all the leg work so I don't have to. Here's her article on Sweet Potatoes vs. Yams. Thanks to her, I learned that what I just ate were Garnet yam and Purple yam. And the ones I got from Trader Joe's were Jewel yams, which are smaller but ultra moist and sweet.
She also has a couple yam recipes there, like Pots de Creme with yams, that I'd like to try someday.