What are “Yoast Merge Tags”?
This is a custom function we have created so that we can configure the Yoast title and description with Brand information and allows us to “spin” the meta tags, so when they are displayed in the SE’s, they will be unique to the brand site.

The following merge tags are available for use within the Yoast SEO fields title and description fields.

##brand_name## – outputs the brand name which is found in the post title.
##brand_country## – outputs the country name.
##brand_phone## – outputs the brand phone number.