What is "Niche" ?

A topic or subject which a website is focused on.
Search is a broad field, but as you drill down each niche consists of many smaller niches. An example of drilling down to a niche market

1. search
2. search marketing, privacy considerations, legal issues, history of, future of, different types of vertical search, etc.
3. search engine optimization, search engine advertising
4. link building, keyword research, reputation monitoring and management, viral marketing, SEO copywriting, Google AdWords, information architecture, etc.

Generally it is easier to compete in small, new, or underdeveloped niches than trying to dominate large verticals. As your brand and authority grow you can go after bigger markets.