A Break of Structure is the market's way of saying "the trend continues."
In an uptrend, price makes higher highs and higher lows. When it pushes up and closes beyond the previous swing high, that's a bullish BOS — confirmation the up-move has more to give. In a downtrend, breaking the previous swing low is a bearish BOS.
Why it matters. A BOS keeps you on the right side. If you're long and the market keeps printing bullish BOS, your thesis is intact. When the BOS stops coming, pay attention — momentum is fading.
The nuance most people miss: how price breaks matters as much as that it breaks. A break driven by a strong, impulsive candle (displacement — next lessons) is real intent. A slow, grinding poke through the level that immediately gets sold is often a liquidity grab in disguise. Same line crossed; opposite meaning.
BOS = continuation. The next concept, CHoCH, is its opposite: the first hint of a reversal.