What is an additional credit cardholder?
This is someone you share your credit card with. Both of you have a card and you share the credit limit.
However, unlike with joint current accounts, where both account holders are liable, the primary credit cardholder is solely responsible for the debt. So as the main cardholder, you will be responsible for any spending made by additional cardholders.
You'll need the permission of the additional cardholder to complete an application.