What it means
Internal breaks happen constantly; swing breaks carry the weight. Take direction from swing structure and timing from internal structure.
In practice
Every large swing is built from a smaller zigzag. Traders who time entries on a lower timeframe watch this inner structure for the first sign that a pullback is ending, such as a small break back in the direction of the main trend.
Keeping the two apart prevents confusion: the swing structure sets the direction and the area to trade from, and the internal structure provides the trigger.
What to watch for
Treating an internal break as a trend change is a common error. Price can break minor structure many times during an ordinary pullback while the main trend stays intact.