"Copyable" text — used for the default new-referral message and each popback step — is the message you intend to copy/paste (or send) when following up with a referral. It supports simple value substitution so you don't have to hand-write each one.
Use ${...} to pull in a value from the referral's form responses:
Hi ${response.first-name}, just following up on your referral!
Inside the curly braces, use response.<field id> to reference an answer, where <field id> is
the Field ID shown in the footer of that question's card in the form builder.
For example, a question titled "First Name" typically gets the field id first-name, so you'd
write ${response.first-name}.
If you're not sure of a field's id, open Organization → Edit Questions and check the small text under the question card — that's the exact id to use.
See also: Building Your Referral Form, Follow-ups (Popbacks).