This file defines modification to stats (Str,Dex etc.) at character creation.
The first row (titles of columns ) is filled by the names of defined characteristics of PC (like MOD_STR = strength modifier).
The first column is filled by race names.
The crossings of the certain identifiers indicate what advantages /penalties receive PC with chosen race - used for character creation.
In BG1 TotS we have:

2DA V1.0
0
           MOD_STR    MOD_DEX    MOD_CON    MOD_INT    MOD_WIS    MOD_CHR
HUMAN      0          0          0          0          0          0
DWARF      0          0          1          0          0          -1
ELF        0          1          -1         0          0          0
GNOME      0          0          0          1          -1         0
HALF_ELF   0          0          0          0          0          0
HALFLING   -1         1          0          0          0          0