FMCL 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 "FIFM Transfer Structure: Leveling 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_FMCL TYPE FMCL.
The FMCL table consists of various fields, each holding specific information or linking keys about FIFM Transfer Structure: Leveling Information data available in SAP. These include BELNR (Accounting Document Number), GJAHR (Fiscal Year), BUZEI (Number of Line Item Within Accounting Document), HKONT (General Ledger Account)... 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. .