What are social signals?
Social signals are how you or your business are perceived on social media. Think of it as your reputation. Having lots of shares, likes and stellar reviews will indicate to search engine providers, such as Google, that you are top notch.
This is important because the search engine providers use these social signals in the algorithms that contribute to your page ranking. Low ratings, for example, equate to lower page ranking and higher ratings equate to higher page ranking.

How do I improve SEO with social media?
One way is to write a blog on your website. Blog posts that are then shared to outside sources, such as Google My Business and Facebook, are the base of what will become the social signals used by search engine providers.
Much like the graphic above, it is a seemingly endless twisting feed that could help drive your page ranking up and subsequently generate new leads.