It's not a single video (and sadly there hasn't been any new content in a year!), but Richard Borcherds's channel has some of the best math content I've seen. If I have to pick one I'll go with this video from his Rings series about Burnside rings and differential operator rings as an illustration of his style; for me, at least, it's a source of excellent insight into fields (cough) I know very little about.