what is niche directory ? whats the diffrence between niche directory and general directory ?

A niche directory is only about one topic like cars or books will only accept sites with content of that nature. A general directory will accept websites with any kind of content.

A niche directories are more focus on regional/local area, their targetable portion are market sector that narrowly defined which have specific group of potential customers.

Niche directories usually focus on a specific topic and are intended to be a larger source of information for that topic than you would find in a general dirctory.