With the Referrer Source persona type you are able to choose from multiple options for your personalization needs:

With the URL option, you are able to select an arbitrary website address referrer to trigger your persona rule. Additional settings are available to fine-tune your selection, including URL Is -- an exact match of the website address, URL Is Not -- does not match a website address, URL Contains -- a website address contains a particular string of characters, URL Does Not Contain -- a website address that does not contain a particular string of characters.

The Page on your website option allows you to pick from a list of pages currently published on your website.

Lastly, the Common Referral Websites option allows you to pick from a list of common referrers, including Google, Facebook, Twitter or Youtube.