What Are Options and How Do They Work?
ES: ¿Qué son las Opciones y Cómo Funcionan? PT: O que são Opções e Como Funcionam
The contract that grants the right to buy or sell an asset at a fixed price: its four parameters, the four basic positions, and what makes it worth what it is worth.
The Definition, and Why Options Exist
An option is a contract granting its buyer the right, but not the obligation, to buy or sell an asset at a set price before a set date. The seller of the option takes on the matching obligation: if the buyer exercises, they must deliver. In exchange for taking it on, they collect a premium up front. That asymmetry — a right for one party, an obligation for the other, a premium as compensation — is the whole structure of the instrument. The most useful analogy is a deposit on a property purchase: you pay a sum to reserve the right to buy at an agreed price; if it suits you, you go ahead; if not, you lose the deposit and nothing more.
The Four Parameters That Define a Contract
Any option is completely described by four pieces of information. The underlying: which asset it is written on — a share, an index, a future, an ETF. The type: a call if it grants the right to buy, a put if it grants the right to sell. The exercise price, or strike: the price at which you will be able to buy or sell. And the expiration: the date the right lapses. To this you must add a detail of size worth internalising from the very beginning: in US equities, one contract controls 100 shares, so a premium quoted at 2.50 actually costs $250.
The Four Basic Positions
With two option types and two sides of the contract, there are exactly four elementary positions, and every complex structure is a combination of them. Buying a call: a bullish bet with loss capped at the premium and potentially unlimited gain. Selling a call: collects premium, wins if price does not rise, and carries theoretically unlimited loss if it rises sharply. Buying a put: a bearish bet or portfolio insurance, with loss capped at the premium. Selling a put: collects premium, wins if price does not fall, and commits you to buying the asset at the strike if it does. The rule that organises all four is simple: whoever buys has defined risk; whoever sells has defined income.
What the Price Is Made Of
An option’s premium breaks into two parts that are always worth distinguishing. Intrinsic value is what it would be worth if it expired right now: for a call, the underlying price minus the strike, or zero if that is negative. Extrinsic value is everything else, and it is what you pay for the possibility that things improve before expiration. That extrinsic value depends on three factors: the time remaining — more time, more possibilities — the implied volatility — how much the asset is expected to move — and, to a lesser degree, interest rates and dividends. Extrinsic value erodes until it disappears at expiration, and that erosion is the source of both the buyer’s main risk and the seller’s main income.
In, At and Out of the Money
The relationship between the strike and the underlying price determines the option’s state and almost all of its behaviour. A call is in the money if the underlying trades above the strike: it has intrinsic value. It is at the money if the two roughly coincide, and that is where extrinsic value is at its maximum. And it is out of the money if the underlying trades below: it has only extrinsic value, and will expire worthless if nothing changes. For puts the relationship inverts. This classification is not decorative terminology: it determines the probability that the option ends up worth something, how much its price will move on a move in the underlying, and how much time decay is at stake.
What They Are Actually Used For
Three functions, worth knowing in this order. Hedging: buying puts protects a portfolio from a decline without having to sell it, the way insurance protects a house without anyone having to move out. Income generation: selling calls on shares you already own, or puts on shares you would like to buy cheaper, turns waiting into a payment. Speculation with defined risk: expressing a directional view while risking a known amount rather than the capital the equivalent position in the asset would require. To these three you can add a fourth with no equivalent in the underlying: trading volatility itself, profiting if the market moves more or less than its price implies.
The Four Basic Positions
| Position | Thesis | Maximum gain | Maximum loss |
|---|---|---|---|
| Buy a call | Bullish | Unlimited | The premium paid |
| Sell a call | Not bullish | The premium collected | Theoretically unlimited |
| Buy a put | Bearish or hedging | Strike × 100 less the premium | The premium paid |
| Sell a put | Not bearish | The premium collected | Strike × 100 less the premium |