What is so special about "NIFTY bank"?

Have you read news articles on the company that could be moving its stock? It looks as though they took a pretty good beating for awhile, perhaps pandemic-related, but it's on the rebound now, either out of optimism for companies in the sector or something in particular involving this company. Perhaps there was some negative news that drove selling and people realize the stock was oversold and therefore a good buy at current prices.

Check around chat rooms and message boards and look for any rumors circulating, because there's a saying in the markets: "buy on rumor, sell on fact." Maybe speculators have heard something that makes this bank attractive, or perhaps optimism about the economy as a whole is driving it upward. After all, overall strength in the economy is good for banks because it drives borrowing.

The point is, there are MANY reasons why this stock is performing this way, and without some research it's hard to give you a more specific answer.

Bank Nifty represents the 12 most liquid and large capitalised stocks from the banking sector which trade on the National Stock Exchange (NSE). It provides investors and market intermediaries a benchmark that captures the capital market performance of Indian banking sector.

https://www1.nseindia.com/live_market/dynaContent/live_watch/bn_home_page.htm

In other words, it's a quick way to evaluate the performance of the Indian banking industry.