A Follow Link is a hyperlink that sends a signal to search engines that it should influence the ranking of the target page.
All hyperlinks be default are follow links. Follow links carry some of the linking domains authority to the linked domain. For example, if NBCSPORTS.COM links to your sports blog, some of the domain authority from NBCSPORTS.COM passes to your blog’s domain. How much depends on the algorithm and ranking factors of the search engine.
If the link comes from a reputable website, a follow link is desirable. But if it comes from a spammy website, the link can harm the linked website.
The opposite of a Follow Link is the NoFollow Link.