This indicator shows the premium index data for the market (only crypto) you're currently looking at.
The premium index is the difference in price between the perpetual swap contract and the spot index price. In plain and simple English: it shows whether the spot market for a specific coin is trading at a discount or at a premium. This is official data from the exchange itself.
At the moment of publishing TradingView only has data for Binance. So only use this indicator on Binance charts right now (USDT perps and BUSD perps). Make sure you're looking at a perpetual swap contract, if you're looking at the spot market for example the indicator won't work.
Once TradingView adds more data like this I'll try to make sure that the logic of the code will also work for other markets.