When you pay a premium for an option, you're buying two things at once: real exercise value, and time. Separating those two is the key to understanding why option prices move the way they do - sometimes against you even when the stock cooperates.
Educational only - not investment advice. Options involve substantial risk and aren't suitable for every investor. Nothing here is a recommendation to buy or sell anything. Examples are simplified and ignore commissions, taxes, and assignment timing. Consider speaking with a licensed financial professional.
Premium = intrinsic value + time value
An option's price (its premium) breaks cleanly into two parts:
Intrinsic value - the exercise value if it expired right now. A $100 call with the stock at $108 has $8 of intrinsic value. An out-of-the-money option has zero intrinsic value.
Extrinsic (time) value - everything else: the premium you pay for the chance the option gains value before expiration. It's driven mostly by time left and expected volatility.
Intrinsic value of a $100 call: zero below the strike, then rises dollar-for-dollar above it. Time value is whatever the option costs on top of this.
Worked example - splitting the premium
Stock is at $108. A $100 call is trading for $11. Intrinsic value is $8 (108 - 100). The other $3 is time value - what the market charges for the remaining chance of further upside. As expiration nears, that $3 melts toward zero.
What moves an option's price
The stock moving - the obvious one. Calls gain as the stock rises, puts as it falls.
Time passing - every day, a bit of time value drains away. This works against buyers and for sellers.
Volatility - when the market expects bigger swings, options get more expensive (more chance of a big move); when it calms down, they get cheaper. This is why an option can lose value even after the stock moves your way - if implied volatility falls at the same time.
The Greeks, gently
The "Greeks" measure how an option's price reacts to those forces. You don't need the math - just the intuition:
Delta - how much the option moves per $1 move in the stock. A delta of 0.50 means roughly 50 cents per dollar. Handily, delta also approximates the rough probability the option finishes in the money - a 0.30-delta call is loosely a "30% chance" bet.
Theta - the daily cost of time decay. A theta of -0.04 means the option loses about 4 cents of value each day, all else equal. Theta is the buyer's headwind and the seller's tailwind.
Vega - sensitivity to volatility. High vega means the option's price swings a lot when the market's volatility expectations change.
Gamma - how fast delta itself changes as the stock moves. Most relevant close to the strike and near expiration.
Why this matters: a beginner buys a call, the stock ticks up, and the call still loses money - then blames bad luck. Usually it was theta (time decay) or a drop in volatility (vega) quietly eating the time value. Knowing the Greeks turns that surprise into something you can anticipate.