What does "Referrer" mean?

We like to encourage people to share your giveaway campaign. After all, this helps you raise more and get more visibility. People have the option to “Share to Enter” when you use the Giveaway style  Sliding Scale. When donors chose "Share to Enter" they are given a unique link to share on social media or via email. When someone enters the giveaway campaign through that link, that person and the referrer will both get one entry to say thanks. This feature is optional and can be turned off.