The Referrals tab will only appear if you have referrals enabled and have given this customer referral cards to hand out.

Fields and options in the Referrals tab include:
Active Cards |
The number of active referral cards the customer has to give out. |
Referrals that came in |
The number of new customers who came in and used one of this customer's referral cards. |
Cards that paid out |
The number of referral cards that generated a rewards card. |
Total Earned |
The amount the referring customer has earned in referral bonuses. |
For more on working with rewards and referrals, see Rewards/Referral Program.