Building Link Popularity is one of the most important and critical aspects of any effective Search Engine Optimization campaign today. The 'off-page' factors such as link popularity, PageRank and Anchor Text in incoming links play a major role in your site's ranking in the search engine results pages (SERP). Search Engines consider your site more important if more links point to your site. Building link popularity improves the PageRank of your web pages (Read more about PageRank). The higher the PageRank of your website, the higher its importance for search engines and higher it gets ranked in the search engine result pages. Search engines also take into account the PageRank of the pages that link to your site and its industry relevance to your own industry. Links from higher PageRank pages and industry relevant sites give your site a higher value.
Link building is very beneficial to the success of a website. When you increase the link popularity, it will help increase your traffic, and search engine ranking. It will also increase your pagerank, but you shouldn't worry about pagerank as it is just a number, and is only valuable if you plan to sell your site to newbies.