Definitions

Referral: where one party is recommended to a second party and both parties are made aware of the fact.
e.g. "I've spoken to Bill from Nice Chairs UK and he is expecting your call."

Lead: where one party may have a lead for, but is not aware of, a second.
e.g. "Bill from Nice Chairs UK might need some IT support."

Recommendation: where one party is suggested as a service provider to a second.
e.g. "Call Bill from Nice Chairs UK for good prices on office furniture."

Tip: a piece of unqualified information that may be of use, to be followed by a cold call.
e.g. "Chair companies use IT systems which may need support."