Niche

niche 

original a french word, which means a segment, section, or space. In older times, it would have referred to an alcove or small discrete space in a room our building where a specific task might be carried out, or where specific things might be stored... a book niche.

In the porn buisness, niche refers to the type of porn, such as teen, mature, fetish, hardcore, etc. There are literally hundreds of different niches in the adult entertainment business, the smaller ones (say, like midget lesbians or Estonian grannies) being refered to as a micro-niche. The fetish market breask down into many sub-niches as well, depending on the type of play and position that the individuals involved enjoy.