What is a No-Follow link?

 nofollow is a value that can be assigned to the rel attribute of an HTML a element to instruct some search engines that the hyperlink should not influence the ranking of the link's target in the search engine's index.

Nofollow provides a way for webmasters to tell search engines. Don't follow links on this page or don't follow this specific link.
Nofollow links do not allow search engine bots to follow links. It does not pass on any link juice.

Nofollow links are links with a rel="nofollow" HTML tag applied to them. The nofollow tag tells search engines to ignore that link. Because nofollow links do not pass PageRank they likely don't impact search engine rankings.

No follow is a link attribute that instructs spiders not to crawl the particular backlink on the webpage. Hence these links are never indexed in search engines. They are only used to build traffic from various external webpages.

This thread is really good to know about no-follow links. I have noticed most high & popular sites always prefer to give no-follow links.

So I just want to now, Getting Nofollow links from high authority sites is still useful?