A call buyer has the right, but not the obligation, to buy the underlying stock at the strike price until the expiration date. If you buy a call option, your maximum risk is the money paid for the option, the debit. The maximum profit is unlimited depending on the rise in the price of the underlying asset. To offset a long call, you have to sell a call with the same strike price to close out the position. By exercising a long call, you are choosing to purchase 100 shares of the underlying stock at the strike price of the call option.
Sellers have obligations.
A call seller has the obligation to sell 100 shares of the underlying stock at the strike price to the person to whom the option was sold, if that person chooses to exercise the call option. Sellers have obligations. If you sell a call option, your risk is unlimited to the upside. The profit is limited to the credit received from the sale of the call. When selling calls, make sure to choose options with little time left until expiration.