Before you can say where price is going, you need to mark where it turned. Those turns are swing points.
A swing high is a candle whose high is higher than the candles on either side — a local peak. A swing low is a local trough. String them together and the market's structure appears: a sequence of highs and lows you can actually read.
Internal vs. external. External structure is the big, obvious swings that define the trend. Internal structure is the smaller swings inside a leg. Confusing the two is the classic beginner error — reacting to a tiny internal wiggle as if the whole trend just changed.
Clean vs. choppy. Some charts have obvious, readable swings; others are noise. When the structure isn't clean, the honest read is "no trade here." A "clean swing points" confluence exists for exactly this reason — you want structure you can trust, not structure you're forcing.
Mark your swings first. Every concept that follows — BOS, CHoCH, liquidity — is defined relative to them.