A Domain describes the value range of a field and is assigned to a data element. All fields that use the data element will have the value range of the domain. The value range is defined by specifying the type and length of the domain. Fixed value intervals can also be defined for the domain and are automatically used as check values on screen entries.
A Data element describes the business meaning of a domain. Information about the meaning of a field such as its label is assigned to the data element and is accessible from all screen fields that use the data element.