This file is not fully understood, but it is thought to control caching of biff files.

The first column the filenames of biff files.
The second column lists the number of valid entries (e.g. 2 means consult the AREARESREF1 and AREARESREF2 columns).
Subsequent columns list biff files to cache the the initial biff is loaded
In BG2: ToB we have:

2DA V1.0
NO_AREA
           NUMBER_AREAS AREARESREF1 AREARESREF2 AREARESREF3 AREARESREF4 AREARESREF5 AREARESREF6 
AREA090A   1          CD3CREA2   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA120A   1          CD3CREAN   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA120B   1          CD3CREA2   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA140A   1          CDCREANI   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA2100   1          CD4CREA3   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA210A   1          CD4CREAN   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA210B   1          CD4CREA3   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA2200   1          CD4CREA3   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA2300   1          CD4CREA2   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA280A   1          CDCREANI   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA290A   1          CDCREANI   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA300C   1          CD3CREAN   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA300E   2          CD3CREAN   CD4CREA3   NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA6000   1          CD3CREAN   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA600A   1          CD4CREA3   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA    
AREA600B   1          CD3CREAN   NO_AREA    NO_AREA    NO_AREA    NO_AREA    NO_AREA