When you search in Google you'll mainly see two type of results: natural links or sponsored links.
Online Marketers pay per click (PPC) on the sponsored links area; these sponsored links can cost from $0.01 to $20.00 per click depending on how much competition there is for that search keyword!
You too could make a great sales page and use Google Adwords to buy traffic to your site but if you get to the top of the natural search results for a keyword then all the traffic is free! This is the aim for being a niche whiz; once the site is set up for appearing high in the natural search results you can kick back, watch the money roll in everyday and perhaps start working on another niche!
I've highlighted the area for sponsored links in Google; it's surprising how many people click on them thinking they're part of the normal search results:
