Meaning
A solid yellow square from the emoji version 12.0 colour set. It means yellow and is a common tile in colour grids and shared game results.
Football fans use it as a yellow card, and players of word-guessing games share result grids where 🟨 marks a right letter in the wrong spot: “Got it in four tries 🟨🟩⬜🟩🟩” It also suits caution notes and sunny pixel art. The round version is 🟡.