What Is an Option?
Calls, puts, and why they exist · 15 min
Comfortable with the stock basics from Investing Fundamentals (what a share is, how prices move) — no options background assumed.
A 2,600-Year-Old Idea
Options feel like a modern financial invention, but they're not. Around 600 BCE, the Greek philosopher Thales of Miletus studied the stars, decided a bumper olive harvest was coming, and acted on it — except he didn't have the money to buy up olive presses outright. So he paid a small deposit for the right to rent them at a fixed price once harvest season arrived. His prediction turned out right, demand for presses spiked, and Thales exercised that right, rented the presses at the price he'd locked in, and sublet them at the much higher going rate. The spread was his profit. Without knowing it, he'd just traded the first option on record.
The modern market traces to April 26, 1973, when the Chicago Board Options Exchange opened its doors — the same year Fischer Black and Myron Scholes published the formula we'll dig into in Lesson 3. Before the CBOE, options changed hands informally between dealers, with no standard terms and nobody guaranteeing either side would actually pay up. The CBOE fixed that: standardized contracts, public quotes, a clearinghouse backing every trade. Day one volume was a modest 911 contracts. Today it's roughly 40 million options contracts trading daily on U.S. exchanges alone.
The Core Idea
An option is a contract giving its buyer the right, but not the obligation, to buy or sell something at a set price, on or before a set date. Every option, no matter how exotic it gets later, boils down to three numbers:
- Underlying (S): whatever the option is written on — usually a stock, but it could be an index, ETF, commodity, or currency
- Strike price (K): the price at which the holder gets to buy or sell, also called the exercise price
- Expiration date (T): the last day the option can be used. Miss it and, if it wasn't exercised, the contract just expires worthless
Whatever you pay to own the option itself is the premium — and it's also the absolute most you can ever lose as the buyer.
Calls and Puts
There are only two flavors:
- A call option gives you the right to buy the underlying at the strike. You want the price to go up.
- A put option gives you the right to sell the underlying at the strike. You want the price to go down.
Every option trade has two sides. The buyer (long) hands over the premium and holds the right to act. The seller (short, or "writer") pockets that premium up front but is on the hook to fulfill the contract if the buyer decides to exercise.
A Concrete Example
Say Apple (AAPL) is trading at $190 and you think it's heading higher before next month's earnings. You buy one call option:
- Strike: $195
- Expiration: 30 days
- Premium: $4.50 per share
Since one standard equity option contract covers 100 shares, that premium costs you $450 total.
Scenario A — AAPL rises to $210 by expiration: you exercise, buying 100 shares at $195 and immediately selling at $210. That's $1,500 gross profit. Subtract the $450 you paid and you've netted $1,050 — a 233% return on the money you actually risked.
Scenario B — AAPL sits at $190 through expiration: the call expires worthless and you lose the full $450 premium. Painful, but notice what didn't happen — you didn't lose anywhere near the $19,000 you'd have been out if you'd bought 100 shares outright and the stock went nowhere.
That asymmetry is the whole appeal of options in one sentence: limited downside, leveraged upside.
American vs. European Options
Options also come in two exercise styles:
- American options can be exercised any time before expiration — most U.S.-listed stock options work this way.
- European options can only be exercised right at expiration, not a day before. Most index options (SPX, NDX) are European-style, and — slightly confusingly — the Black-Scholes formula we derive in Lesson 3 is technically built for European options only.
The right to exercise early is genuinely valuable for puts, especially deep in-the-money ones, but rarely worth much for calls on stocks that don't pay dividends. We'll come back to exactly why in the Binomial Trees lesson.
Intrinsic Value vs. Extrinsic Value
Every option's premium is really two things stacked together:
- Intrinsic value — what you'd pocket if you exercised this instant. For a call: max(S − K, 0). For a put: max(K − S, 0). It's never negative; the worst case is zero.
- Extrinsic value (or "time value") — everything left over. It's the market pricing in the chance the option gains more intrinsic value before it expires, driven mostly by how much time is left and how volatile the stock is.
Concrete example: AAPL at $190, a $185-strike call trading at $9.00. Intrinsic value is $5.00, so the remaining $4.00 is extrinsic value. An option should always trade at or above its intrinsic value — if it didn't, you could exercise and resell for a free, instant profit, and the market doesn't leave that sitting around for long.
Moneyness
"Moneyness" is just a way of describing where the stock price sits relative to the strike:
- In-the-money (ITM): positive intrinsic value. Call: S > K. Put: S < K.
- At-the-money (ATM): S ≈ K. Intrinsic value is close to zero, but this is where extrinsic value peaks for a given expiration.
- Out-of-the-money (OTM): zero intrinsic value. Call: S < K. Put: S > K. What you're paying for here is pure time value — essentially a bet that the stock moves far enough, fast enough.
Deep OTM options are cheap in dollar terms but extremely leveraged — a $0.10 option that pays off $5 hands you a 50x return. They're also the most likely to end up worthless: CBOE data puts the share of options held to expiration that expire with zero value above 70%.
Why Options Exist
Strip away the speculation and three legitimate uses actually drive this market:
- Hedging: a fund manager sitting on 10,000 shares of Apple might buy puts as insurance against a crash — a small, known premium in exchange for capping how much they can lose.
- Speculation: traders use options to bet on direction or volatility with a defined, capped downside and outsized leverage.
- Income generation: shareholders sell covered calls against stock they already own, collecting premium as income in exchange for giving up some of the upside if the stock rips higher.
Knowing which of these three a given trade actually serves matters more than it sounds — the exact same instrument, a put option, can be portfolio insurance for a hedger, a leveraged short bet for a speculator, or a cash-secured income play for a seller, all at once, depending only on who's on which side.