Nofollow links attributes do not allow search engine bots to follow the link. That means if the website owner is linking back to you with Nofollow attributes, it does not pass on link juice. Only Humans will be able to follow the links.
Whereas the Dofollow links allow the search engine to follow them and reach your website. Giving your website link juice and a backlink. If a webmaster is linking back to you with this link both Search Engine and Humans will be able to follow you. Link juice in SEO refers to the value or equity passed from one page or site to another. Search engines see links as votes by other websites that your page is valuable and worth promoting.
An example of Nofollow Link:
<a href=”http://www.google.com/” rel=”nofollow”>Google</a>
An example of Dofollow Link:
<a href=”http://www.google.com/”>Google</a>
Note: By default all the hyperlinks are Dofollow. So, you don’t need to do anything to make a link do-follow.