option premium based on Spot or future?

1.Option Premium are based on future price or spot price ? I need to find the ITM options and OTM options. Basis means difference between spot and future.
2.Some say that call options are based on future price and put options are based on spot price ?
3.also what is the meaning if difference between spot and future increases (basis increases) and basis decreases ? specially in banknifty, we can see huge difference in spot and futures … almost more than 100 points ?