What's the difference between Niche Marketing, Mainstream, and mass marketing?

i've already explained niche marketing to you (it's where you advertise or create clothing targeted towards a specific "group" of people, such as goths or preps). not sure on mainstream, but i think that it's more like...trendy stuff. mass marketting it advertisement towards the population as a whole.. kind of the opposite of niche marketing. again, i could be wrong on all of that. it's better to search on yahoo, or another respective website. you could probably even use dictionary.com to get the "definitions"

update: yep, dictionary.com worked.

Mainstream;
1.) the principal or dominant course, tendency, or trend
Example: the mainstream of American culture.
2.) belonging to or characteristic of a principal, dominant, or widely accepted group, movement, style, etc.
Example: mainstream Republicans; a mainstream artist.

Mass Marketing:
1. the production and distribution of a product intended to be sold to a relatively high proportion of the population.

Niche Marketing:
1.) the production and distribution of a product intended to be sold to a specific proportion of the population.