Nifty/Bank Nifty future
Stock options are of 2 types i.e. call option or put option. Call option allow the buyers the rights, but not the liability to buy given quantity of the latent asset, at a given price on or before a given future date. A Put option allow the buyer the rights, but not the liability to sell a given quantity of the latent asset at a given price on or before, a given date.
Options may also be sold short, in this case the seller of a call option has the freedom of delivering the parts of stock and the seller of a put option has the obligation of purchasing shares of stock. Because you are inducing an obligation when you sell an option contract, your capability incurs substantial risk.