Source report tells you from where your respondents visit and take your survey.
You may see "Direct link" which means respondents click on the survey URL directly to take your survey.
You may also see "facebook.com" which means respondents saw your survey on facebook and clicked on it to take it.
Please note: Due to users' settings, our system may sometimes fail to get the exact url of upstream webiste. In this case, the source will be displayed as "Direct link".