All license plates that aren't in the six- or seven-digit alphanumeric sequence determined by your state are, by definition, vanity plates.
Here's how you tell . . . if you got to pick what your plate says, you have vanity plates.
Even if they say "I LV GOD" or "BIBLE," they're considered "vanity plates."
I know I know. It just doesn't seem to fit the literal definition of a 'vanity' plate to have JOHN316. 'Personalized' plate would be better.