Off page optimization
This is about working with something that is one of the single strongest ranking factors, links.
When you get a link to your page from another website, you have very simply explained "got a voice" on your business. In the past, it was about quantity, to get as many "votes" as possible. Today it is more about getting as strong a voice as possible for the best results.
In fact, a "bad voice" from a website flagged as spam can actually have a direct negative impact on your SEO.