They define the link as do follow. Also if you do not use rel attribute the link will be treated as ‘dofollow’. Dofollow links allow search engines and humans to follow them to reach websites.The dofollow links count as votes for your site’s authority, and they pass along “link juice”. So if you receive a link from a high-authority website, you will appear to be a more credible source, and it will boost your SEO efforts.