Backlinks are incoming links to a website or web page. The number of backlinks is an indication of the popularity or importance of that website or page. Search engines, such as Google, Yahoo!, and Bing, often use the number of backlinks that point to a website as one of the primary factors for determining the importance of the website and, consequently, its ranking in the search engine results. The ever-popular Google PageRank algorithm, for example, uses backlinks to determine the relative importance or PageRank of a website.
To check how many backlinks are pointing to your website, check your domain name on the All-in-One SEO Checker tool, and then check the value that appears under Incoming Links for Google and Bing.