Is a billion a million million, or one followed by twelve noughts (1,000,000,000,000) or is a billion a thousand million? Same thing for a trillion. I think t

Is a billion a million million, or one followed by twelve noughts (1,000,000,000,000) or is a billion a thousand million? Same thing for a trillion. I think the first is or maybe was a UK'ism. Maybe the rest of the world does that too?