I'm aware of no difference. When it comes to RESPA Section 8 I believe they are synonymous. Look at §1024.14:
(b) No referral fees. No person shall give and no person shall accept any fee, kickback or other thing of value pursuant to any agreement or understanding, oral or otherwise, that business incident to or part of a settlement service involving a federally related mortgage loan shall be referred to any person. Any referral of a settlement service is not a compensable service, except as set forth in §1024.14(g)(1). A company may not pay any other company or the employees of any other company for the referral of settlement service business.
(f) Referral. (1) A referral includes any oral or written action directed to a person which has the effect of affirmatively influencing the selection by any person of a provider of a settlement service or business incident to or part of a settlement service when such person will pay for such settlement service or business incident thereto or pay a charge attributable in whole or in part to such settlement service or business.