PrestaBay — PrestaShop eBay Integration has build-in variables engine. Using this engine you can use special variables in multiple places of the module and it will be replaced with corresponding data from PrestaShop product.
One of the examples is "Description Template". At the bottom of the template, you can find a drop-down box with a list of all supported variables. If you select one of the options and click on "Insert" you will get special variable tag inside "Description Template". Like [product_name] or [product_description]
Another example, fields "Item Title" and "Item Subtitle" inside "Selling Profile".
The third most common place is the custom data field from "Item Specific".