What is Banknifty

please tall me what is bank nifty and how to tred in bank nifty using zerodha kite app

Bank Nifty is a sectoral index, representing the 12 most liquid and large capitalized stocks from the banking sector.

You cannot directly trade the Index, to trade in Bank Nifty there are Futures and Options contracts. If you are new to trading would suggest you read the following modules on Varsity on Futures and Options: