Open interest shows whether money outflows or inflows into the derivatives market, and it is a reliable preliminary indicator of the mid-term Bitcoin trend.
Explaining Open Interest in the Futures & Options Markets
Open interest refers to the total number of derivative contracts (futures or options) that remain active at the end of the trading day. Note, that the number of outstanding futures/options contracts is not a fixed number and changes by the day. That number changes as some traders open new positions and others close their existing positions. In short, open interest indicates the total number of options or futures that have not been yet settled.
Perpetual Swaps are derivatives offered by the OKex exchange and trade similarly to Bitmex Perpetual Contracts. Again, they are like Futures Contracts, but without expiries and daily settlements.