Talk allows you to communicate with certain monsters. Some monsters can even carry on interactive conversations. If you supply a keyword, the monster may be able to give you some more information about it.

Examples :

:talk scribe
The scribe says to you, "<Yawn> You bore me.".
:talk scribe bore
The scribe says to you, "Yes, you are a boring fellow.  I see no reason
  to continue a rational discussion with you."