Back linking - can you tell me why it works?

Right, BUT you're not building backlinks for a niche. You're building backlinks for a keyword. There are billions of keywords, so you can see how quickly that cuts down the competition.

 

Back links are vote to your website, as many quality websites you connect your websites ranking would be stronger in Google and other search engine.

There are some basic consideration that you have to follow those are only dofollow backlinks would be advantageous for this purpose.

If you manage to take back links from high PR sites and aged domain then these back links would be counted as quality back links.

You should build back links following relevancy that is find those website which are dealing in the same niche as your website is.

 

Backlinks are the route through which both search engines and people find your site. Without them there are no roads to your city, no goods coming in, and no marketability for you. I don't know how I went from web marketing to city building, but you get the drift.