When a user clicks on a link on a webpage and the browser takes the user away
to the next URL, it sends the new URL a Referer: header in the new request
telling it where it came from. That is the referer header. The Referer: is
misspelled but that is how it is supposed to be.
With curl you set the referer header with -e or --referer, like this:
curl --referer http://comes-from.example.com https://www.example.com/