Something new on NFC capability on iOS12?
Basically two new NFC features were released - however they are only available on select newer phones, so there's not really any change if you have an older phone.

The new features are available on iPhone XS, iPhone XS Max and iPhone XR.

Feature 1: Express Card

This makes it possible for the phone to work as a NFC card for stuff like student cards, entry cards, transportation tickets - when the battery is dead! The idea is that even when the phone is shut down due to lack of battery, the phone can still be used as a valid NFC card for approx. 5 hours.

The feature is only available for (few) select cards that are stored in the Wallet.

Feature 2: Background Tag Reading

The phone is now always "listening" for NFC tags. You can read a tag without unlocking your phone, and it will show a small notification that you can activate to go into the app that is registered to handle that type of NFC tag.

Previously you had to open the app first, and then read the tag.