Dofollow links pass along what the SEO community commonly calls “link juice.” Links are a vote for quality. By learning which webpages are often linked to, search engines can determine how highly websites should rank in search results.
When Google bots are crawling a website they look for external links point to other websites. If this links is “do follow” then search engines will follows the link and so link juice gets passed.
Do follow links are the commands to search engine robots to follow that link for spiders crawling process.do follow count as back link to the site from search engine. It's important for site ranking to get quality back links.
The Do follow link will pass page rank. It allows both user and search engine to reach the site it point to and it is highly recommended by search engine i.e, Google, Yahoo, Bing.
Backlinks are the external links from different websites pointing to your website. This is one of the most important factors out of the total (almost 200) factors which search engines consider for ranking your site in SERP.