The number of unique domains linking to your website. A single domain may link to you more than once.
The more unique domains that link to your website, the better you'll do in the search engines. So make sure you're using various resources, not just one website/friend who links over-and-over again. That doesn't count!
“Spartan Spark’s general CRM system and their entire platform was a complete game-changer for management of contacts, management of leads. Their entire system for web presence and digital marketing was why we hired them in the first place.”” -Kimberley Simonson, Marketing Manager, One Eye Industries.