Can you differentiate between ‘nofollow’ and ‘dofollow’ link?
 

Nofollow links are not passed by search engines bot and therefore cannot be cached or indexed. Dofollow link is a kind of hyperlink and it passes through all search engines and it puts an impact over page rank.

No follow and do follow are link attributes. No follow links are never crawled and indexed in search engines, whereas do follow links are those that are crawled and indexed in search engines.

The main purpose of Nofollow attribute was to retain authority and PageRank. Google still crawls the links, but Matt Cutts said they don’t include them in their overall graph. However, nofollow links provide some SEO value and have hidden power.

But as per now, dofollow or nofollow links don't matter at all. The only thing is relevant links connecting to other pages.

@alizine you said the right thing and i appreciate your answer.

no follow links are not crawled by search engines whereas do follow links are crawled by search engines.

Google caches only do follow link where as it doesn't caches no follow links . So its good to submit your info on high pr do follow websites

Dofollow Link: Dofollow links allow google(all search engines) to follow them and reach our website. Giving us link juice and a backlink.

Nofollow Link: Nofollow link attributes search engines bots do not follow for the link follow. The website owner is to have the nofollow attributes by linking again he will not pass the link juice.

Nofollow links : 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.

Dofollow links : Dofollow links allow google (all search engines) to follow them and reach our website. Giving us link juice and a backlink.

To Follow Or Not To Follow, That Is The Question
So now that you know the difference between do follow and no follow links, which should you use on your site?
To know that, you really need to think about what sites you are linking too in your posts. The vast majority of them will probably be do follow links, as only by linking out to sites will you get sites linking back to you. Make sure that your do follow links are relevant to your post, anything that isn’t relevant could look spammy to search engines.
For anything that isn’t relevant, yet you want to include a link, a no follow link would be best. Also, make sure that any advertising links, affiliate links, sponsored links, etc. are no follow. You still get paid when people click on these links, but you don’t need search engines to follow them.
Another useful use of the no follow tag is when mentioning competitors. You may want to point out something on their site that is of worth, yet not want to pass any link juice. That is a call you have to make.
Lastly, if you run more than one website and want to link to each other on every page (perhaps in the footer), you’d probably be best making it a no follow link. Search engines may view it as being spammy if you use a do follow link for the same site on every page

NoFollow & Dofollow. Nofollow links attributes do not allow search engine bots to follow link.That means if the website owner is linking back to you with nofollow attributes, it does not pass on link juice.

Nofollow links attributes do not allow search engine bots to follow link.That means if the website owner is linking back to you with nofollow attribut

Best description I have heard yet...SEO advice...Find the dofollow links associated with your competitors and get linked to those same sites

everything is explained above what i would to add that do-follow links is a ranking factor whereas no-follow link do not contribute towards the website ranking.
What as far as my experience i found no follow back links are great source of traffic as all the good blogs and forums give no-follow links to your website

Dofollow links: Crawler will visit the link and then will index it.
Nofollow links: Crawler won't visit the link hence it won't be indexed.