One can see the URL of the site (also called referrers) which pushed the visitor to your site.The site owner can also share links to non-website based sources such as chat software, email etc.I was trying to understand how can one track non-website based referrers in Google analytics such as:User coming from email linksUser clicking from chat messages
Tracking referrals from non-internet resources
google analytics;referrer
You have to add URL parameters to track a visitor from external sources that do not provide referrer data.this may help you:https://support.google.com/analytics/answer/1033867?hl=en