With the exception of the SY structure, there are no built-in complex data types in ABAP. Therefore, complex data types must either be programmer locally or defined in the Dictionary. If you want to combine a new local complex data type from other data types, use the TYPESstatement as a construction rule.
On the one hand, you can construct the new complex type according to the known type in the case of TYPE or LIKE reference to a known complex type. When you refer to the complex ABAP Dictionary types Structure or Table Type, which are based on elementary Dictionary data elements, the structure from the Dictionary is used, and the data elements are converted into elementary ABAP types.