What is the difference between value and empty_value in xml customization files?
value for input fields stands for predefined value, it will be displayed initially and customer/staff may change it.
empty_value is more a hint for what should be filled in an input field. Once customer/staff puts cursor to this field, the empty_value text disappears. Example: when you add new customer account, 'First Name', 'Middle Name' and 'Last Name' empty_values are displayed in Name fields. Once you start writing, the text from these fields disappears.