NPC Dialogues
A NPC Dialogue is build up of triggers and responses. The response can be a combination of chat message and a response script build of Response Operations.
Dialogues can either be build from KAs defined in npc_triggers table or in KA Scripts defined in quest_scripts table with quest == -1 or from Quests.
Here is a list of the KAs we have in the game, and the ones we would like to have.
References
Debugging in game
You can see which KA the NPCs has using /info on him.