Buy order - Buy order placed by FIIs (it may also be short covering order)
Sell order - Sell order placed by FIIs (it may also be long un-winding)
(all these are as per NSE data)
Buy% - on a whole (buy+sell orders)
Total OI - Total outstanding positions of FIIs
OI% change - from Previous day OI
Index long%, Call long% and Call writing% - based on Total OI
you can get all these data in a file in the given below link of NSE: (in the link download participant wise OI and FII derivatives statistics file:
https://www1.nseindia.com/products/content/derivatives/equities/homepage_fo.htm