Create documentation on merge duplicate form fields

I would like to know what "merge duplicate form fields" actually do. Under openmrs/admin/forms/auditField.form, if we merge duplicate form fields, what actually happen? What other impacts we need to know? How does it affect existing forms?

I am not able to find any documentation on that. It would be helpful to have such so that implementers know what it is about and whether they should merge duplicate form fields.