For example, if you believe the share price of a company currently trading for $100 is going to rise to $120 by some future date, you’d buy a call option with a strike price less than $120 (ideally a strike price no higher than $120 minus the cost of the option, so that the option remains profitable at $120). If the stock does indeed rise above the strike price, your option is in the money.
The price you pay for an option, called the premium, has two components: intrinsic value and time value. Intrinsic value is the difference between the strike price and the share price, if the stock price is above the strike. Time value is whatever is left, and factors in how volatile the stock is, the time to expiration and interest rates, among other elements. For example, suppose you have a $100 call option while the stock costs $110. Let’s assume the option’s premium is $15. The intrinsic value is $10 ($110 minus $100), while time value is $5.
When buying or selling options, the investor or trader has the right to exercise that option at any point up until the expiration date - so simply buying or selling an option doesn't mean you actually have to exercise it at the buy/sell point. Because of this system, options are considered derivative securities - which means their price is derived from something else (in this case, from the value of assets like the market, securities or other underlying instruments). For this reason, options are often considered less risky than stocks (if used correctly).