A Link Building specialist will help generate traffic to your site. By generating traffic from either social media, or using purchasing power to buy links from other sites and companies, SEO Link specialists can help develop your page to gain traffic.
They can either accumulate this is in good faith, by adding meaningful content, that your audience is going to enjoy, which will help your site rank higher, when your SEO is implemented correctly. SEO good house practicing tends to fare better for search engines to crawl on your website.