Strike price is the price at which that specific derivative contract can be executed. In case of call option, strike price is the price at which the call buyer can buy the stock. Whereas in case of put option, strike price is the price at which the put buyer can sell the stock. In our example of the call option contract between Sita and Noor, strike price was Rs 1.1 crore.
Generally retail clients take long position in the option contracts and institutions take the short position. Strike with highest call OI indicates the price level at which institutions have sold a lot of call options, thus it means institutions don’t feel that price will go above this particular level. This level indicates the maximum upside. For example if in case of Maruti, Rs.7800 represents the strike with highest call OI, then it means that institutions expect the price to remain below 7800.