The volume of BANKNIFTY INDEX FUTURES is 1.87 M.
Open interest is the number of contracts held by traders in active positions — they're not closed or expired. For BANKNIFTY INDEX FUTURES this number is 1.94 M. You can use it to track a prevailing market trend and adjust your own strategy: declining open interest for BANKNIFTY INDEX FUTURES shows that traders are closing their positions, which means a weakening trend.