Do Follow means linking of a website but allow the crawler to recognize that link. Do follow allow the link juice to gets passed.It helps to achieve higher page rank. Do follow does not allow the link juice to gets passed.It does not affect the Page rank.
No-Follow means linking of a website but instructs search engine crawlers not to follow that link. No follow attributes do not pass any link authority or link juice to the linked website. These links are commonly used for user-generated content, sponsored links, or any other link that you don't want to give SEO value to. No follow links do not affect the page rank of the linked website.