This indicator generalises the idea of MACD to take any arbitrary series available on the chart, using input.source values.
To provide an overview of the MACD indicator:
You have two EMAs, one with a faster period, usually 12, another with a slower period, usually 26.
You calculate a MACD line, by doing (fastEMA - slowEMA)
You then calculate a Signal Line by taking a moving average of the MACD line over some period.
With this indicator, you can analyse momentum between any 2 series (not just EMAs), they could be raw close prices, other moving averages on the chart including specialised ones, that most MACD implementations won't provide a facility for, for example Kaufman Moving Average.
The chart shows this indicator sourcing 2 inputs from the chart:
A Hull Moving Average as the fast series
And a Simple Moving Average as the slow series
It then calculates the MACD (Series1 - Series2), and a Signal line from the resulting MACD.
A signal series is still calculated manually by the indicator, and thus will be restricted to the provided moving average options (this indicator provides a few like EMA, SMA, Hull, and so on).
Uses of this indicator are essentially what you will use a MACD for:
Evaluate momentum of a strength.
Crossover Signals: MACD vs. Signal, MACD vs. Zero Line, MACD Histogram gradation.