Forza (line) above 0 means EURO is stonger than DOLLAR
Momento (histogram) above 0 means EURO has a positive momentum against DOLLAR
The added value to see and directly on EURUSD chart is that indexes consider also other pairs so their and has a larger view on forex markets.
Script has also an option for multi timeframes.
I think that could be used as filters for LONG or SHORT positions in lower time frames.