A call option gives the owner of the option the right (but on the obligation) to buy something for a fixed price (the strike price) up until the day the option expires. The option owner usually pays something to enter into the option contract. The payment is called the premium.
For a call option on a stock to have value at its expiration, the price of the stock would have to be greater than the strike price of the option. At that point, one could use the option to buy the stock at the strike price and then immediately sell the same stock in the stock market. Otherwise, the option expires worthless.
Someone takes the opposite of every option trade. Someone writes the options that other people buy. Option writing is the opposite of option buying. The payoffs are opposite, too.
Whereas the call option buyer usually pays a small premium for an unlikely but very high return, the writer of the same option earns a small premium for taking on the risk of an unlikely but very large loss. What happens to the stock price determines who wins or loses in the deal.
Success in writing options starts with knowing how to price options. The cost of an option is the probability-weighted expected loss of the option. One needs a good option pricing model to determine the expected loss. Then one must refuse to write options that don’t offer premiums significantly higher than the expected loss (cost) of the option. If the expected loss (cost) of the option is $1.50 per share, perhaps one should refuse to write options with premiums below $1.90 per share. That way, one enters into the deal with an expected profit. Whether one achieves an actual profit depends on what happens to the stock price.
Success in writing call options also depends on risk management. Option writing carries the risk of an occasional but very large loss. Too much bad luck could be ruinous. Effective diversification is essential.