A backlink is a hyperlink from one site to another with weight redirection. Search engines like Google use the backlink as their Page Rank rating. When a site links to another, it means that they consider it worthy of attention, and such chains force search engines to pay attention to the site that received the link and possibly change their position in the search. Links from trusted and authority resources or domains help sites to move up in the search, this is also called — link building. Link building is one of the most important parts of website SEO.