I'm not sure what you are asking for. you havent really given much of a description. But I'll take a stab at assuming you are asking for the ability to add TAGS or INDEX-KEYWORDS to each post.
The forums have a search feature which can be used for searching for posts with desired qualities. In addition, forums can be created and grouped in such a way that everything related to ENGLISH or CHINESE or GAMES or COFFEE can be put in to its own forum/category, as the forum admin as created and setup for those types of discussions.
