Bjoern it actually is a credit card. The difference is small because of how bunq implemented it. Let me try to clarify.
"Normal" creditcard gives you a spending limit of say something like €1000,--.
When you use the cards the spending limit is lowered accordingly, say I spend €200,- then my remaining spending limit is €1000 - €200 = €800,--.
At the end of the month they will make up the balance and you pay the bill from your bank account. Either you pay everything directly, or you can't pay everything at once and instead you pay in instalments for instance (or whatever other arrangement you have).
Now, this €1000,- spending limit is based on a creditworthiness check, as it is basically a loan from your creditcard issuer. You could pay stuff but then in the end you can end up in a situation where you can not pay the bill at the end of the month.
Now with bunq you can't get loans/credit whatsoever as bunq does not believe in that.
So you get the "creditcard" (Travel card).
The spending limit of this card is equal to the balance of your bank account (IBAN). When there's €500,-- in your account then the spending limit is also €500,--.
When you use the cards the "remaining spending limit" (read: account balance) is lowered accordingly, so when you buy something of €100,-- your remaining limit (the balance) will be €500 - €100 = €400,--.
This money is taken out of your account immediately, this way bunq knows for sure that you will be able to pay (it's basically reserved).
At the end of the month bunq will send out "the bill" as well, but since all transfers have been reserved already you won't have to pay anything anymore. So no unexpected charges or chances of going in the "red numbers".
Using this construction (providing your own loan basically) bunq can distribute the cards as "creditcards". A merchant can't see who's providing the credit. They won't notice the difference.
I hope the above clarifies the Travel card construction a bit more and shows how it is an actual credit card (without credit). 😁