> For the complete documentation index, see [llms.txt](https://870.gitbook.io/knowledgebase/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://870.gitbook.io/knowledgebase/how-do-options-work/reading-option-tables.md).

# Reading Option Tables

 More and more traders are finding option data through online sources. While each source has its own format for presenting the data, the key components generally include the following variables:

* Volume simply tells you how many contracts of a particular option were traded during the latest session.
* The "bid" price is the latest price level at which a market participant wishes to buy a particular option.
* The "ask" price is the latest price offered by a market participant to sell a particular option.
* Implied Bid Volatility can be thought of as the future uncertainty of price direction and speed. This value is calculated by an option-pricing model such as the Black-Scholes model and represents the level of expected future volatility based on the current price of the option.
* Open Interest number indicates the total number of contracts of a particular option that have been opened. Open interest decreases as open trades are closed.
* Delta can be thought of as a probability. For instance, a 30-delta option has roughly a 30% chance of expiring in-the-money. Delta also measures the option's sensitivity to immediate price changes in the underlying. The price of a 30-delta option will change by 30 cents if the underlying security changes its price by one dollar.
* Gamma is the speed the option is moving in or out-of-the-money. Gamma can also be thought of as the movement of the delta.
* Vega is a Greek value that indicates the amount by which the price of the option would be expected to change based on a one-point change in implied volatility.
* Theta is the Greek value that indicates how much value an option will lose with the passage of one day's time.
* The "strike price" is the price at which the buyer of the option can buy or sell the underlying security if they choose to exercise the option.

{% hint style="info" %}
Buying at the bid and selling at the ask is how market makers make their living.
{% endhint %}