Let’s make a folder. Name it test.txt. Open it, and place test.txt inside it. Now, open two finder windows (this is easiest, I would suggest just dragging up after clicking the triangle if you’re in list view if you know how) and drag test.txt (the file) to the folder containing the folder named test.txt. This will confuse the OS, probably because it wants to replace the parent folder with the exact same name file.
Nobody will ever google for this.