This is a powerful indicator to guage the strength of the market.
1) By default it plots the momentum of the number of stocks in Bank Nifty that are above 20 period MA. You can change the MA number if you desire. 2) It also has other features like plotting the above along with the weights allocated in index / MACD of the number of stocks above and below index / cumulative raw index with respect to number of stocks above / below MA. 3) You can use it to other indices as well but can add only 12 stocks participating in any index.
How to use it?
If you see the price moving up (down) but the index (Item no. 1 above) falling (rising), it indicates higher chance of reversal.
If shorter momentum crosses longer momentum from below, it usually signals bullish and vice versa.
As always use this indicator in tandem with other indicators.