Once you add the Google Analytics Tool within DTM by giving the account ID for both staging and production, it automatically acts as a page load rule and will trigger a default tag which you will be able to observe in any debugger.
In addition to that, if you want to capture any new attributes or variables on any specific pages, that's when you will create a new page load rule and configure accordingly.
You can do it by creating a new page load rule in DTM, use a condition which matches the product page where a product is viewed. then, you can add under events a category, action, and label (Ex: prodView as a category, View as Action and the Product Name as a label.
you can simply use custom variables Name & Value and under Name, you can use the product name and under the value, you can add a counter or prod view.
For any of these, you can create data elements within DTM and you can use them while populating these values in GA page load rule.