Black lentils are also known as Beluga Lentils. Many people say they look like Beluga Caviar.
They taste pretty much the same as regular lentils, just slightly different. I don't know how to explain it. Lentils are very nutritious, a good source of protein and fiber, and the black lentils just make your plate look more interesting. We eat with our eyes!
I used to be able to buy them at Whole Foods but now I just buy them on Amazon since I can't find them anywhere else.