If Nifty is presently at 8050, then 8000 Calls is called in the money (because if the option expires now, there will be an intrinsic value, Rs 50 in this case), 8050 calls is at the money( no intrinsic value, but strike price and market price same) and 8100 call is called out of the money because it has no intrinsic value.
Similalry, 8100 puts is ITM, 8050 Puts is ATM, and 8000 puts is OTM