Linking is the important part of Search Engine Optimization, either your linked to another site or your being linked by another site. Links in your blog or content, by default are dofollow. If its tagged with rel = nofollow, then it is nofollow link. The difference between them is explained below: If site with high DA or PA is linked with you, google increase your authority for dofollow links. But if it has used nofollow tag then google wont increase your authority.

Nofollow links attributes do not allow search engine bots to follow link. That means if the website owner is linking back to you with no-follow attributes, it does not pass on link juice.
Dofollow links allow google (all search engines) to follow them and reach our website. Giving us link juice and a backlink.

Difference plays a big role in your ranking.

Dofollow is simply the default state for a link. In another way, any link without the nofollow attribute is a dofollow link.

When another website links to you with a standard (aka dofollow) link, it can directly affect search engine rankings. because this link passes link equity from the linking page.

Nofollowed links are the hyperlinks with a rel=“nofollow” tag in HTML code of the link.

These links do not help you in the search engine rankings of the destination URL because Google does not transfer link equity.

It doesn’t matter anymore. A Penguin update a year and a half ago made spammy back links irrelevant instead of harmful… That is unless you get a manual penalty but you’d have to have a lot more than just a high ratio of Dofollow links

Dofollow and nofollow backlinks are two different ways to identify a link and inform Google how to associate the website you’re linked to with your own. A dofollow link helps a website gain authority, whereas a nofollow link does not pass on link juice.

Dofollow and nofollow backlinks are two unique ways of distinguishing a connection and illuminate Google how to relate the site you’re connected to with your own. A dofollow interface helps a site gain authority, though a nofollow connect doesn’t pass on connect juice.