While the importance of back-links, as Google sees it, has diminished somewhat in recent years, there’s no doubt back-links are still the most critical aspect of any SEO strategy. Why? Google needs some method of determining which sites are more important than others.
To help make this computation, it looks at the back-links from other sites to your site. Each link counts as a “vote” for your site. But, don’t be fooled, Google is not democratic – each vote/link doesn’t count equally. In the past, when they were more equal (but not exactly equal), people would build links from all sorts