As explained in the “What is Traffic Source?” FAQ, if there is not a custom Traffic Source rule for the given referring URL, then the Traffic Source will be set to the domain name of the referring URL. For example, let’s say your website is Sports.com. A user can navigate to your website by clicking on a link to it from the “https://bluetriangle.com/industry-benchmarks/banking/” URL. The Sports.com page would then have a document.referer of https://www.bluetriangle.com/industry-benchmarks/banking/. The Blue Triangle tag does not have a custom Traffic Source rule for a referring URL of https://www.bluetriangle.com/industry-benchmarks/banking/, so in this case the Traffic Source would get set to the base domain of bluetriangle.com.