Referral Traffic is come to all your SEO backlinks which is used to click on your main website, it is called a Referral Traffic.

Referral Traffic!!!
 

In these traffic describe the visitors to your site come from direct link on other websites,these traffic also helpful to improve the business point of view

“Referral traffic is used to describe visitors to your site that come from direct links on other websites rather than directly or from search engines.

eHow Definition: “Referral traffic is used to describe visitors to your site that come from direct links on other websites rather than directly or from search engines.” ... One site refers traffic to another site