This is what the referral code is all about
The Oral B Recommendation Code is requested when registering as a customer at https://shop.oralb.de/ and implies that there is a discount if you have a referral code.
Unfortunately, the programme is not active at the moment and existing customers of the shop cannot refer new members and pass on discounts. Generally, an existing customer can pass on a referral code to other people and will receive credit for it - the new customer will also receive a discount (between 5,-? and 15,-?). As can be seen in the screenshot, existing customers have the option to see account credit, but not to generate a code.
Also check out Amazon for good deals on Oral B (advertising links).