What is dofollow or nofollow backlink

When a link is created on top of  a webpage, crawlers come and read that link. Not only is this link made for crawlers but also for humans. So that human can click on that link and go to another webpage. That is, one link surveys two people  fast is crawlers and second one is user. So if it is a dofollow backlink, crawlers follow that link. If it is a nofollow backlink, then crawlers do not follow it. Rather, the user goes from one page to another by clicking on both. Basic  different of Dofallow or Nofollow backlinks. Search engines like dofollow backlinks, if our website gets dofollow links from anywhere, then it is a good signal for search engines. And it helps in Seo off page. Nofollow backlinks do help in Seo off page but do not provide our website as good value. If you want to do guest posting of your website  like Seo,  backlinks so please connect our site..