Each type of Resource defines Resource Fields that correspond to some data from the external system. For example, you can create a to Resource Field and use that as the destination email address in an 
Email Resource.
Once added to a 
Form, you can map Resource Fields to the Form's 
Fields and 
Table Columns. When the Resource interacts with the external system these Resource Fields automatically read or update the values in their mapped Form Fields and Table Columns accordingly.
Resource mappings can be configured by right-clicking on a Resource in the 
Resources View and selecting 
Show mappings for resource.
Here you can configure which Fields and Table Columns map to which Resource Fields. The Auto-map button maps Fields and Table Columns to Resource Fields with the same name.
Fields can be imported into a Form from a Resource by clicking on the 
Import From External Resource button in the Fields View. This creates Fields in the Form with the same name as the selected Resource Fields. All Fields added to the Form this way are automatically mapped to their corresponding Resource Field in the Resource.