Meaning
A solid green square, part of the emoji version 12.0 colour set. It means green and usually stands for correct, complete or good.
It is the star of progress bars and habit trackers, and in word-guessing grids it marks a letter in exactly the right place: “Water intake this week: 🟩🟩🟩🟩🟩⬜⬜” It also builds grass and trees in pixel art. Compare ✅ for a single done item and 🟢 for a round dot.