@RP3436 "tag" is an identifier you can give to uniquely identify a particular order or categorizing a set of orders etc. Check out the documentation here.
@Vivek @All - Is Kite Java API paid API? I mean , i have tried to get #private and #public key/token , it takes me to a window to but some 2000 credit..? Please assist?
You can use postbacks. You need to setup endpoint to accept post request and Kite trade will send postbacks like this. You can go to developers console and set postback URL.