What is a "Niche"

(Often pronounced as neesh or nitch)

A niche market is the subset of the market on which a specific product is focused. The market niche defines the product features aimed at satisfying specific market needs, as well as the price range, production quality and the demographics that it is intended to target. It is also a small market segment.

See Wikipedia for a more complex overview
To quickly simplify the above here are some Niches and sub-niches: - 
Main Niche "Craft work"
Sub Niche "Knitting"
Sub sub Niche - "Knitting - Jumpers"
The same principle applies across hundreds of different topics, from Sport, Music, Fashion, Science, Hobbies... we hope you understand us on the subject of "Niches"
A niche is a specialized market that targets a specific audience and customizes its products to meet this audience’s needs. 

 

What truly separates one niche from another is the people who buy these products. For that reason, approach the niche-searching process with this in mind:
It’s not the product or service, it’s the people who use it that defines a niche.
 
There’s a person behind every purchase, so think of your niche as a group of people who have at least one common interest, problem, or need.