Swing highs and swing lows are the turning points that define the staircase of a trend.
A swing high is a local peak — a bar whose high is higher than the bars on either side of it. A swing low is the mirror — a bar whose low is lower than the bars on either side. These are the 'steps' of the trend staircase from lesson 3. In an uptrend, each swing high is higher than the last (= higher high), and each swing low is higher than the last (= higher low). In a downtrend, both get lower. Learning to spot these turning points on a chart is the single most useful skill at this stage.
Every time price makes a peak and starts to fall, that peak is a swing high. Every time price makes a dip and starts to rise, that dip is a swing low. The chart zigzags between these turning points.
SH = swing high, SL = swing low. HH = higher high (a swing high that's higher than the previous one). HL = higher low (a swing low that's higher than the previous one). In an uptrend, you keep seeing HH and HL — that's the staircase going up.
Why people mix it up: Both have 'high' in the name. Beginners use them interchangeably, which creates confusion when reading trading content.
How to tell them apart: A swing high is ANY local peak (a turning point where price goes from rising to falling). A higher high is a swing high that's ABOVE the previous swing high. Every higher high is a swing high, but not every swing high is a higher high — it could be a lower high instead (meaning the trend may be weakening).