Here you can find how nifty theory works:

The Nifty Dow Theory is a technical analysis tool used to forecast trends in the stock market. It is based on the premise that the market has three trends: primary, secondary, and minor. The theory uses the movement of the Nifty index in India and the Dow Jones Industrial Average in the United States to identify trends in the market. The theory suggests that when both indexes are moving in the same direction, it indicates a trend in the market, while a divergence between the two suggests a potential reversal.