EXTR_LIST 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 "Field List for ALV Representation in Extract Management" 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_EXTR_LIST TYPE EXTR_LIST.
The EXTR_LIST table consists of various fields, each holding specific information or linking keys about Field List for ALV Representation in Extract Management data available in SAP. These include HASHV (Hash encryption of selection criteria), COUNTERV (Sequence number with same hash code), RGJNR (Report Group), HASH (Hash encryption of selection criteria)... 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. .