Meaning
This flag stands for Saint Martin, the French part of a Caribbean island that it shares with Sint Maarten, the Dutch part to the south.
It appears in beach holiday posts, Creole and French food in Grand Case, and island hopping, with 🏝️ or 🍽️. Sint Maarten has a separate flag emoji, so pick the side you mean. “Lunch at the lolos in Grand Case 🇲🇫🍽️”