# What is a Variable?

* A variable is a container or a placeholder for a data value with a specified type.
* Variables may contain values that can be used in Actions.
* A variable has a lifetime which is referred to as scope. The scope defines the accessibility of the variable to a specific Container Action, Action box, or all Action boxes.
* A variable can be defined in shared Variables, an Action box, or a Container Action (where possible). Shared Variables are defined in the “Variables” tab.

{% embed url="<https://media.langstack.com/documentation/media/images/code/training_manual/chapter_2/ch2whatisavariable_img1.png>" %}

* Shared Variables scope covers the execution of all Action boxes.
* The scope of variables defined in an Action box includes all the Actions in the Action box.

{% embed url="<https://media.langstack.com/documentation/media/images/code/training_manual/chapter_2/ch2whatisavariable_img2.png>" %}

* The scope of the variables defined in the Container Actions includes all contained Actions for duration of the execution of the Container actions.

{% embed url="<https://media.langstack.com/documentation/media/images/code/training_manual/chapter_2/ch2whatisavariable_img3.png>" %}

* A variable can be Read Only. If specified as "Read Only," it takes the value initialized the first time and cannot be assigned any other value later.

{% embed url="<https://media.langstack.com/documentation/media/images/code/training_manual/chapter_2/ch2whatisavariable_img4.png>" %}

* A variable can be List type and can contain multiple values of the list type. These values can be accessed by their index number starting from 0 (zero). To define a variable as a list, set the checkbox \[X] List as in the image below.

{% embed url="<https://media.langstack.com/documentation/media/images/code/training_manual/chapter_2/ch2whatisavariable_img5.png>" %}

* Variables with a complex type may require other settings e.g. setting the Sample schema for the Json type.

{% embed url="<https://media.langstack.com/documentation/media/images/code/training_manual/chapter_2/ch2whatisavariable_img6.png>" %}

**Sample Schema for JsON**:

{% embed url="<https://media.langstack.com/documentation/media/images/code/training_manual/chapter_2/ch2whatisavariable_img7.png>" %}