# Data layer and data types

The data layer represents all your available data. It consists of **information about your site** (e.g. page name, product ID) **and your visitors** (e.g. user ID, customer status) in the form of **JavaScript variables**.

![](https://2673302412-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LdtBYhZj-wxWhoZaUXI%2F-LnwHdtRw4yl1HGXdBjr%2F-LnwHnkG24LUsJSq1bef%2FDATALAYER%5B1%5D.png?alt=media\&token=22b30e4b-f4b6-4ece-b0b0-92c5a84c42fb)

These variables have two uses:

– To populate the tags present in your container;

– To create activation rules for your tags.

Additional information:

The data layer can consist of two types of data:

– Data implemented by your IT department or your technical provider for all your web pages, based on the CSS, Backoffice and CRM. These data are called “**external variables**” and are displayed in your site’s source code as a **JavaScript object** containing all the variables used by your tags.

This is what the external variables look like in the source code:

![](https://2673302412-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LdtBYhZj-wxWhoZaUXI%2F-LnwHdtRw4yl1HGXdBjr%2F-LnwHwRte906k9ppIAyZ%2FEXTERNAL_VARS_SOURCE_CODE-1024x583%5B1%5D.png?alt=media\&token=4f4b7f9c-daf7-4e99-a719-f985fc739d66)

– Data created in the interface by **Commanders Act staff** or **TagCommander** users based on information available on the site’s pages (URL, cookies, HTML tags, external variables in the data layer, etc). They are called “**internal variables**” and are displayed in the **TagCommander container’s code**.