Referring Domains tool lists all domains referring to the researched domain, along with number of backlinks from each of these domains, their Flow Metrics and Alexa Rank. The referring domains are sorted in a descending order based on the number of backlinks the researched domain has received from them.
Alexa Rank is a traffic metric which estimates the domain’s traffic rank based on 3 months of historical traffic data collected from the users of Alexa Toolbar. The algorithm takes into account the domain’s traffic sources, unique visitors, and page views, as well as the number of visitors and number of page views of all the sites with Alexa Toolbar installed. The lower the score, the more traffic-driving the domain is. NA would indicate there’s not enough data to calculate the traffic rank for the domain, or the domain doesn’t have the Alexa toolbar installed.
Serpstat Page Rank (SPR) - a score on scale from 0 to 100 which measures the page authority. Serpstat Page Rank predicts how influential a URL might be based on the number of pages linking to it. Links are not measured with equal weight, so a strong link will have a relatively stronger influence on URLs.
Serpstat Trust Rank (STR) - a score on scale from 0 to 100 which measures the site authority based on how authoritative and trusted are the sites linking to the site in question. A site closely linked to trusted site can obtain higher trust rank scores, while a site which has some questionable links would get a much lower score.