Meaning : A person whose case has been referred to a specialist or professional group.
Example :
The patient is a referral from Dr. Bones.
Meaning : A recommendation to consult the (professional) person or group to whom one has been referred.
Example :
The insurance company says that you need a written referral from your physician before seeing a specialist.
Meaning : The act of referring (as forwarding an applicant for employment or referring a matter to an appropriate agency).