A dofollow link is a hyperlink that Google considers to be a vote of confidence for the website it links to. In other words, getting other websites to link to your website is like giving your website a vote of confidence from an external source.
And the more votes of confidence your website has, the higher it will rank in Google search results.
Dofollow links are contrasted with nofollow links, which are essentially “votes of condemnation” from external sources. Google doesn’t count nofollow links as votes of confidence, so websites that rely heavily on nofollow links for SEO purposes tend to rank lower in search engine results pages.