
What exactly is this supposed to be and how does it function
The Mask ID needs to be configured for dynamic barcodes like (Weight embedded, price embedded, coupon codes etc). Masks are used to define the format and mark characters will help you define the place of each property in the barcode.
Please refer to the following article for more details https://learn.microsoft.com/en-us/dynamicsax-2012/appuser-itpro/setting-up-bar-codes