Yeah I use it for my Apple Watch and recently added my wife’s iPad to it.
Basically it’s a set monthly installment that sits as a full balance on your cc. It charges every month and is included in your required monthly minimum payment.
The downfall (IMO) is that you can’t simply pay it off early.. you have to pay off your regular balance, and then pay it off. And if you have multiple Apple Card installments, you can’t pick which one you pay off? It just sort of asks how much you want to put towards the total of your balances. Idk. Weird.