Backlinks have been around since the late 1990s, that’s almost like since Larry Page and his Co-founder Sergey Brin build the core of Google’s algorithm. Search engine treats links as a vote for popularity; It simply means the more websites that are linking to you the more importance search engine will associate to your website. The search engine crawlers use complex algorithms to carry out nuanced evaluations of web pages based on links pointing to websites.
Link building itself is the process of acquiring or building quality relevant links to your website for better ranking on Search Engine Results Pages (SERPs). Links can also be earned when others are linking to your content. The links pointing to your web page is also known as inbound links.