It’s this. A cipher with a MAC or authentication (like an AEAD) will return “TRUE” and the data that was definitely decrypted properly. A normal cipher just re

It’s this. A cipher with a MAC or authentication (like an AEAD) will return “TRUE” and the data that was definitely decrypted properly. A normal cipher just returns data and it has no idea if it was decrypted correctly, so if you decrypt ABC and it should be XYZ, the wrong key will still “work” but the data will be X@9 which means nothing to you. Normally, you would validate your data after encryption. Like using something “Here is my result, and it has to start with the ascii characters of a valid date.” An authenticated cipher allows you to not care or have to know anything about the data at all, they’re nice. With the downside that you also need to supply the MAC or TAG or SIG along with the data package.