To me, art is when you make something your own, creating something unique that has meaning to you. Craft seems more like the process of doing something. I would say you could teach someone craft, but you can’t necessarily teach art. For example, in the context of bookmaking, I think that the actual work of learning/making different book forms, stitching, trimming, etc. is craft. But then what you do beyond that to make your book different/unique/meaningful is art. Going back to the subject of the video, nail art, I think that it is both a craft and an art, depending on what level you take it to. Craft and art aren’t really interchangeable terms, but they do depend on one another. You have to learn the basic skills of painting/writing/sculpting/whatever before you make a masterpiece.