RFCAT_FLDCAT 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 Catalog - Structure for Field Catalog Text Table" 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_RFCAT_FLDCAT TYPE RFCAT_FLDCAT.
The RFCAT_FLDCAT table consists of various fields, each holding specific information or linking keys about Field Catalog - Structure for Field Catalog Text Table data available in SAP. These include APPLICATION (Application), COMPONENT (Component), COMPVARIANT (Component Variant), FIELD (Field 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. .