About What is a Niche Market

Today, to success on the Internet you must know what is niche markets more?
Definitions of Niche market on the Web:
1.A niche market is a focused targetable portion (subset) of a market.
http://en.wikipedia.org/wiki/Niche_market
2.a relatively small and specialist, yet profitable, market
http://en.wiktionary.org/wiki/niche_market
3.The area of a target market where a company or product is particularly strong. This specialization often results in super
high quality by [...]