Meaning
The flag emoji for Bouvet Island, a remote, ice-covered and uninhabited island in the South Atlantic that is a dependency of Norway. It uses the Norwegian flag, red with a blue cross outlined in white.
Since nobody lives there, it mostly shows up in geography quizzes, trivia about remote places and flag-collecting jokes: “Quiz time: which island flag 🇧🇻 looks exactly like Norway’s?” For Norway itself, use 🇳🇴, which looks the same.