When price closes beyond the most recent swing high or low, confirming the trend is continuing.
In an uptrend, a break of structure is a close above the last swing high; in a downtrend, a close below the last swing low. It confirms momentum in the existing direction.
A BOS tells you the trend is intact and can be used to stay with it or to time continuation entries on the pullback that follows.
Mark the recent swing points, then watch for a decisive close beyond the relevant one — a wick through it that closes back inside does not count as a confirmed break.
A BOS in the trend direction is continuation; a break the other way is a change of character (CHoCH), which is different. Distinguish them by which direction the level breaks.
Reading a definition is step one. Chart Bound drills you on spotting Break of Structure (BOS) and dozens of other setups on live candles, and the Daily gives you one fresh chart to read every day. Free to start.