The main difference between dofollow and nofollow backlinks is the way search engines treat them.
Dofollow backlinks are links that pass "link juice" or SEO value from the linking website to the linked-to website. When a search engine crawler comes across a dofollow backlink, it will follow the link and credit the linked-to website with the same authority and relevance signals as the linking website.
On the other hand, nofollow backlinks are links that do not pass any SEO value or link juice to the linked-to website. When a search engine crawler comes across a nofollow backlink, it will not follow the link or credit the linked-to website with any authority or relevance signals from the linking website.
Nofollow backlinks were introduced by Google in 2005 as a way to combat spammy link building practices. They are typically used for links that the website owner does not want to endorse, such as paid links or comments on blogs or forums.
In summary, dofollow backlinks can have a positive impact on a website's search engine ranking, while nofollow backlinks do not directly affect SEO but can still provide referral traffic and other indirect benefits.