Economics. I never understood it that well having taken two years of high school classes for law and government, then watched a single Economics Explained video and understood so much that I hadn’t understood before.
I skimmed through the channel and believe it's this one based on the fact it had Japan in it and was recent, but I might be missing something. Titles and thumbnails change often as a form of clickbait and that gets confusing when going back to something.