Backlinks are the incoming links to a Website or Blog. The Quantity and Quality of backlinks are very important for Search Engine Ranking. Its Can makes your Website Popular. You can count it as Health or strength of your Site/blog. When Search Engine Calculates the relevance of a site to a keyword, they consider the number of Quality Backlinks/Inbound Links to that website. previously i got an amazing PR Chart which shows the importance of Backlinks.
Lets Have a Look :
Image Credit : LinksManagement.com