"Niche" is a business term meaning a product designed to appeal to only a small section of the population. *They generally have limited distribution--ie. not available in a lot of places. *
What you call "ordinary" in perfumes would be two main categories--designer (developed by design houses--Gucci, Burberry, Hermes, etc) and they are generally available in "better" department stores. *The other would be "mass market" which are generally available in many places like drug stores and discount stores.