BAPIACHE03 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 "Posting in Accounting: Incoming Invoice (Header)" 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_BAPIACHE03 TYPE BAPIACHE03.
The BAPIACHE03 table consists of various fields, each holding specific information or linking keys about Posting in Accounting: Incoming Invoice (Header) data available in SAP. These include OBJ_KEY (Reference Key), OBJ_SYS (Logical system of source document), USERNAME (User name), HEADER_TXT (Document Header Text)... 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. .