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.
An index future is a derivative, similar to a stock future, whose value is dependent on the value of the underlying, in this case, the index like the S&P CNX Nifty or BSE Sensex.
Forex (FX) is the market in which currencies are traded. The forex market is the largest, most liquid market in the world, with average traded values that can be trillions of dollars per day. It includes all of the currencies in the world.