What is the difference between a referral link and a referral code?

What is the difference between a referral link and a referral code?

For prospective customers who click on the referral link, sign-ups will be attributed to the corresponding affiliate. The referral code, on the other hand, can be used by prospective customers upon checkout without going through the referral link.
 
Note that the referral code supersedes the referral link. To illustrate, a customer signs up to Kwik.insure via Affiliate A’s referral link but proceeds to buy a product using Affiliate B’s referral code upon checkout. Affiliate B then gets the referral fee from this transaction.