Model: A mathematical formula used to calculate the theoretical value of an option. This is a mathematical formula designed to price an option as a function of certain variables - generally stock price, striking price, volatility, time to expiration, dividends to be paid, and the current risk-free interest rate. The Black-Scholes model is one of the more widely used models.

Option: A contract that gives the owner the right, but not the obligation, to buy or sell a particular asset (the underlying stock) at a fixed price (the strike price) for a specific period of time (until expiration) . The contract also obligates the writer to meet the terms of delivery if the contract right is exercised by the owner.

Theoretical Option Pricing Model: The first widely-used model for option pricing. This formula can be used to calculate a theoretical value for an option using current stock prices, expected dividends, the option's strike price, expected interest rates, time to expiration and expected stock volatility. While the Black-Scholes model does not perfectly describe real-world options markets, it is still often used in the valuation and trading of options.