# Variables

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## Variables

To a computer programmer, a variable is a symbol in code that can be used to represent a value that will change. A Tag Manager variable performs that same function. Tag Manager variables are used in both triggers and tags:

* **Variables in triggers** are used to define filters that specify when a particular tag should fire.\
   *Example: Fire a pageview trigger when the url variable is “example.com/index.html”.*
* **Variables in tags** are used to capture dynamic values.\
   *Example: Capture and apply the transaction value and products purchased to a conversion tag.*

Tag Manager provides a set of commonly-used [built-in variables](https://support.google.com/tagmanager/topic/7182737) in each container. You can create additional [user-defined variables](https://support.google.com/tagmanager/topic/9125128) to suit your specific requirements.