The Data Layer is a JavaScript object that sends data about user interaction and eCommerce events in your Magento 2 store to Google Analytics 4. It makes it easier to capture intricate data like product information, transaction details, and user behavior, which can be further used in GA4 for precise tracking and insights.
You can also get our Magento 2 GA4 with GTM Extension to setup GA with GTM in Magento 2.
Read this How to Setup Magento 2 GA4 (Google Analytics 4) with GTM guide to setup this extension.
Here are the few more resource to help you get most out of this Magento 2 GA4 with GTM Support Extension.
How to Add Google Analytics 4 (GA4) with GTM in Magento 2
How to Use GA4 with GTM Extension for eCommerce store
How to Add Google Analytics in Magento 2
How to Add Google Tag Manager (GTM) to Magento 2