Meaning
A small red triangular flag on a pole, like a marker on a golf course or a pin on a map. It means a marked spot, a warning or something that needs attention.
Online it is best known for the slang “red flag”, a warning sign in someone’s behaviour, especially in dating: “He said he never says sorry 🚩🚩🚩” It also marks locations, deadlines and reported issues. The opposite slang, a green flag, is often shown with 🟩 or ✅.