Web referral lead is a specific lead source indicating that the lead was generated when a user navigated to your website using a referring link on another site and filled out the Web-to-Lead form containing the Salesforce.com tracking code.

For example, if a user is browsing your partner's website and clicks on a link to your website, then fills out your Web-to-Lead form, a Web referral lead is generated. The lead source details include the referring URL for each Web referral lead.