Domain - Specifies the technical attributes of a data element - its data type, length, possible values, and appearance on the screen. Each data element has an underlying domain. A single domain can be the basis for several data elements. Domains are objects in the ABAP Dictionary.

Data Element - Describes the business function of a table field. Its technical attributes are based on a domain, and its business function is described by its field labels and documentation.

Aggregate Object – Views, Match Code and Lock objects are called aggregate objects because they are formed from several related table.