There are 3 types of structure: Swing, Internal, and Fractal.
Swing -> BOS -> candle body close
Internal -> i-BOS -> candle body close
Fractal -> f-BOS/CHoCH (fractal structure trend change) -> wick break
CHoCH (Change of Character) -> signals internal pullback starting/ending
i-BOS (Internal Break of Structure) -> signals swing pullback starting/ending