VPK_INPUT_SELECTION 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 "All Data Selection Fields" 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_VPK_INPUT_SELECTION TYPE VPK_INPUT_SELECTION.
The VPK_INPUT_SELECTION table consists of various fields, each holding specific information or linking keys about All Data Selection Fields data available in SAP. These include POSNR_FROM (Sales Document Item), POSNR_TO (Sales Document Item)... 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. .