Merge Fields are used to incorporate various listing or product specific fields into your listing template. This allows you to create one template that feels customized to any products the template is applied to.
You will see a list of merge fields on the left hand side to choose from for your template. Merge Fields are storefront specific, so be sure to select a storefront from the "Storefront" drop-down.
You can use the Merge Fields on the left hand side to merge attributes at the product level in your template. If you change the storefront for your template and choose 'save', the merge fields will adjust based on the storefront you choose.
For example, the merge field [NAME] in the template will display the product name on your storefront.