During the middle Ages, the pope could have enormous power (see crusade). Theoretically, there is only one pope. However, several times during the middle Ages there were multiple popes, each of which claimed they were the legitimate and rightful pope. The ones who eventually lost are known as antipopes. Inded, there was even a period in which, later critics were to claim, the papacy was controlled by the female members of a Roman aristocratic family, who variously seduced incumbents, or controlled the Roman mob and thereby the cardinals-elector (on the occasions when elections took place, as opposed to the position being in effect sold in advance, with the electoral college simply being asked to assent to a fait accompli).
A pope is properly addressed as "Your Holiness".
It could be observed that popes who are called Pius or Innocent are neither Pious nor Innocent.