Backlinks are the most important part of SEO. If you wanted to rank your website on search engines like Google, Bing, you have to create a good amount of links. Backlinks are also known as in coming link, in bound link etc. In the basic concept of backlink in SEO is any link that come from any other top-level website to your site is backlink. It comes with the juice of authority and traffic from that website.
Search engines like Google and Bing use the number of backlinks as authority factor to determine that website’s search engine ranking, popularity. Google’s concept of their page rank system is that Google translate a link from page X to page Y as an authority, for page Y, by page X.