What's the difference between VIP Credits and store credits?

A VIP Credit can be used to purchase any outfit or item worth up to £80! You'll be charged for a credit when you don't skip the month or if you return a full purchase made with a VIP Credit (e.g. both items of an outfit). Store credit is issued whenever you make a return and will be issued if you buy an outfit with a VIP Credit and only return part of your order.