What is Open Interest and how is it different from volume?

Open interest is the total number of outstanding futures contracts/swaps, while trading volume is the total trading volume of futures contracts and perpetual swap over a specific period of time.

The above chart highlights few price levels when OI on XBTUSD swaps on Bitmex was either too high or too low. Its from the chart that $1B has been a level of local tops.

There is very less data available publicly about history of OI on Bitmex for XBTUSD. I was also able to get one relevant tweet where one of the trader had mentioned about a big move incoming because of high OI and sideways movement for a long time.

Below is the chart showing it was a local top at that time.

In my opinion, high OI is just a sign of a big move happening soon and if it has confluence with resistance levels, price action, volume etc. it can be a local top

Long term I am bullish and you can follow the chart I had shared on twitter few days back: