AD01FIELDS 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 "DIP profile: Field information" 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_AD01FIELDS TYPE AD01FIELDS.
The AD01FIELDS table consists of various fields, each holding specific information or linking keys about DIP profile: Field information data available in SAP. These include FIELDNAME (Field Name), FPOSITION (Position of the field in the table), ROLLNAME (Data element (semantic domain)), DOMNAME (Domain name)... 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. .