A backlink is a hypertext link on another website that points back to your website. Backlinks are also called "inbound links", whereas a link on your website pointing to another website is called an "outbound link".
Backlinks are important for two reasons:
First, they bring traffic to your website as web visitors to other sites follow the links to your website.
Second, as we have learned, Google and the other search engines examine both the number and quality of inbound links as a measure of a page's quality. Sites with high numbers of quality inbound links are seen as more valuable and are ranked more highly.
Google simply employs the inherent democracy of the Web; sites that other webmasters have linked to are most likely to be the better pages on the Web and so they represent better quality content. Google states, "Pages that we believe are important pages receive a higher PageRank and are more likely to appear at the top of the search results"....