SGX is an acronym for Singapore Stock Exchange. SGX Nifty is listed on Singapore Stock Exchange and follows movements of Nifty (while Indian Stock Exchange NSE is open) or shadow movement of Nifty (while the markets are closed).

Another thing to note is that SGX Nifty is a futures contract and hence its movements are more aligned with Nifty Future contract of that specific month rather than Spot price of Nifty.