A referral is when your website was posted
somewhere else (ie. another web page) and a person clicked on that link to go to your web page. This number is important for the relationships you have with other people. If someone is referring people to your site, it could be strategic to form a relationship with them because they like what you’re doing.
Having referral traffic is good, but extremely hard to build and takes time to cultivate. This percentage will most of the time be lower than other sources.