TechCrunch does a good job here of going beyond the basics, and answering some of the more detailed questions about how some e.g. the virtual card aspect of the card, works.
Perhaps the biggest security feature of the offering is that Apple Card can generate virtual card numbers for online non-Apple Pay purchases. Though Apple said that the app would display your card info during the event, they weren’t specific on what that info would be so I got some more detail here. The physical Apple Card, of course, has no number. The app displays the last 4 digits of the card number that is on the mag stripe of the card only, you never see the full card number.Instead, Apple provides a virtual card number and virtual confirmation code (CVV) for the card in the app. You can use this for non-Apple Pay purchases online or over the phone. This number is semi-permanent, meaning that you can keep using it as long as you want.