When we go to the path
/admin/structure/types/manage/article/fields and use the
Add new field option or the
Add existing field option, does that create a field, create a field instance or attach a field instance? How to differentiate between them? So, programmatically, when to use field_create_field, field_create_instance and field_attach API?
In the field API documentation it only mentions the admin UI and never talks about the path where to create both fields and field instances. So it's confusing. I don't even know if I even make sense.