Closely Related, though Distinct from Futures Contracts, Are the Financial Contracts Known as Options

Closely related, though distinct from futures, are the financial contracts known as options. In essence, the buyer of a call option has the right, but not the obligation, to buy an agreed quantity of a particular commodity or financial asset from the seller (‘writer’) of the option at a certain time (the expiration date) for a certain price (known as the strike price). Clearly, the buyer of a call option expects the price of the commodity or underlying instrument to rise in the future. When the price passes the agreed strike price, the option is ‘in the money’ — and so is the smart guy who bought it. A put option is just the opposite: the buyer has the right, but not the obligation, to sell an agreed quantity of something to the seller of the option.

—Niall Ferguson, The Ascent of Money: A Financial History of the World (New York: Penguin Press, 2008), 227.