It is just a classification of the NPC. So Conversational as opposed to Combat or Custom. Have a look on the NPC rules pages to have a better idea of what each type means, and what they do/will do. May also answer some of your future questiosn as well.
There is no need to change your topic titles to "DELETE" after they are answered. In fact, the opposite is true - it is better to leave your topic well labeled so that other individuals who may have the same question may be able to find it and save from having to create their own thread.
"May the Grace of Ara go with you, and His Vengeance be wrought upon your enemies."