How does Link Building affect SEO? Links are the #1 ranking criteria in every major search engine. Search engines look at every link on the web as a type of vote that is being cast for the web page the link points at. The more links you have from other websites directed to your page, the more authority your page will have in the eyes of search engines.
Unlike a democracy, however, every link does not carry equal weight. The more authority a page has, the more authority that page can pass along with their links. With a smaller number of links on-page, a higher value is passed with each link. Understanding exactly how much value is passed with each link is far beyond the scope of this website, and is a matter of some debate among SEOs.
The text used by other websites to link to you matters a great deal. If someone gives you a link that says "Click Here!", while that is a very encouraging call to action for human visitors, it doesn't give any useful information to search engines about your website. Anchor text leading to your site lets search engines know what you are all about. If you sell pizza for instance, it would be in your best interest if links to your website all said "Best pizza ever", "Pizza in YOURTOWN",or even "YOURBUSINESSNAME." Whatever the links leading to your website say, search engines will rank you a bit higher for those terms. Ideally through Keyword Research you will discover *exactly* the terms you want your business to rank for, and make an effort to get anchor text with those terms whenever possible.