Standard Field Names
Using First Name as an example, the Field Name will be First Name and the System Usage Field will be Contacts First Name. Using the drop-down menu you are able assign the system usage field so anytime a prospect enters their first name, it will correctly populate the system usage field.
This set of field names can be quickly accessed when creating and editing lists, creating form fields, using email personalization and other areas in the application where field names can be selected.
To set up standard field names, see this page.