This file is used to assign dialogue files to PNPCs in game . The dialogues consist of interactions with main character or between party members.
The first column indicates the name of NPC (death variable).
The second one assigns the DLG file with needed dialogues.
The third one is available only in ToB - assigns DLG file for NPC in ToB.
In BG2 ToB we have:

2DA V1.0
 NONE
             FILE	   25FILE
AERIE       BAERIE	  BAERIE25
ANOMEN      BANOMEN	  BANOME25
CERND       BCERND	  BCERND25
EDWIN       BEDWIN	  BEDWIN25
HAERDALIS   BHAERDA	  BHAERD25
JAHEIRA     BJAHEIR	  BJAHEI25
JAN         BJAN	  BJAN25
KELDORN     BKELDOR	  BKELDO25
KORGAN      BKORGAN	  BKORGA25
MAZZY       BMAZZY	  BMAZZY25
MINSC       BMINSC	  BMINSC25
NALIA       BNALIA	  BNALIA25
VALYGAR     BVALYGA	  BVALYG25
VICONIA     BVICONI	  BVICON25
YOSHIMO     BYOSHIM	  BYOSHIM
IMOEN2	    NONE	  BIMOEN25
SAREVOK     NONE	  BSAREV25