[kartan]

> How do you use this physical ID card online?

You don't. For that, you can get a digital signature. You can go to a police station, or to an embassy and present your physical Id card to get a digital signature. You can use that signature to sign contracts or your tax returns.

> how do you apply for a credit card or similar online?

In Spain, with your usual bank, you use your login/password and your 2FA.

In Sweden, you can use Bank-Id almost everywhere to identify yourself. It is also a digital signature, but it has brother use.