I've heard of it, and I think I've heard of the cashback card.
It's just a prepayment card that looks like it combines all the separate gift cards onto one card, which is a great idea, because before, you would have to buy different cards for different shops and to get any meaningful saving, you'd need lots of different cards and carefully manage the amounts so you don't end up with money on cards at shops you aren't planning to use. So a lot of work to get a decent reward. But if you can use the card at a wider range of shops, a lot easier to manage.
But be aware that most discounts are nowhere near 12%, you can use them at the supermarkets, M&S, Amazon etc, but you'll only get 1 or 2% discount. But then again, if you can get 2% off your weekly shop, that could be a couple of quid every week, which adds up over time in an 'every little helps' sort of manner.