MACD subtracts a 26-day exponential moving average from a 12-day one. A 9-day average of that difference is the signal line. The gap between MACD and its signal line is the histogram.
A positive histogram means short-term momentum is stronger than its own recent average. A negative one means momentum is fading. It turns before price does, which makes it a useful early read on whether a move is accelerating.
Pulse uses one simple question: is the histogram above zero? It is one of the five yes-or-no trend checks, worth 4 points of the 20 available for trend.