Paypal is having a targeted promotion to their users.
If you are selected, you will see a giftcard of $10/$15 under you Wallet section on Paypal.

1) Log into PayPal (www.paypal.com)
2) Click wallet (https://www.paypal.com/myaccount/wallet)
3) Scroll all the way down, and you'll see the giftcard (Only if you were targeted)
4) Redeem on eBay or load onto your PayPal account