Links are still the lifeblood of Google as they have been since day one. However, the company is obviously way more sophisticated and can measure the links usefulness. Long story short, a link helps from an authority site or page that Google trusts. Google trusts, who it trusts, trusts. Be careful to use naked links (the URL.com) as opposed to heavy anchor text links. A small percentage of anchor text with keywords is ok and natural. The links should be from relevant pages with high authority. There are tools that measure authority, But they are often inaccurate or not update. You can guess that a link from Twitter or Instagram probably is useful. Look at relevancy, authority and how active is the link? How often is it clicked helps.
Contributors: Tim O’Keefe from Spider Juice Technologies