My understanding is that there's two different types of verification.

Self-verification means that any new secondary devices you log into your account with will need to be verified by an existing login by way of an automatic popup that asks if you trust the device. It used to just be a Yes/No button but I think now they've added QR codes and/or emoji matching.

The other kind is verification between two different people, like when starting a direct message conversation, you might get the same emoji matching window to verify each other.