Open interest is the number of contracts held by traders in active positions — they're not closed or expired. For Gold Futures this number is 15.68 K. You can use it to track a prevailing market trend and adjust your own strategy: declining open interest for Gold Futures shows that traders are closing their positions, which means a weakening trend.
Buying or selling futures contracts depends on many factors: season, underlying commodity, your own trading strategy. So mostly it's up to you, but if you look for some certain calculations to take into account, you can study technical analysis for Gold Futures. Today its technical rating is buy, but remember that market conditions change all the time, so it's always crucial to do your own research. See more of Gold Futures technicals for a more comprehensive analysis.