BAPI_0036_HEADER_ADD is a standard SAP Structure so does not store data like a database table does. It can be used to define the fields of other actual tables or to process "GM: additional header data" Information within sap ABAP programs. This is done by declaring abap internal tables, work areas or database tables based on this Structure. These can then be used to store and process the required data appropriately. i.e. DATA: wa_BAPI_0036_HEADER_ADD TYPE BAPI_0036_HEADER_ADD.
The BAPI_0036_HEADER_ADD table consists of various fields, each holding specific information or linking keys about GM: additional header data data available in SAP. These include REF_DOC (Reference Document Number), OBJ_SYS (Logical system of source document), OBJ_TYPE (Reference Transaction)... See below for full list along with technical details, documentation, text table, check tables, foreign key relationships, conversion routines, relevant tcodes and example ABAP select code etc. .