Is there a actual job description? I know it sounds like I am being rude but seriously since I am not Cathlic, I honestly don't know. Can he be fired? Or is there a blood line?
Popes serve until they either die or resign. When a Pope dies or resigns, the College of Cardinals, which is a group of around 120 very senior clergy from around the world who are given the title of Cardinal, gather together at the Vatican in Rome to pray for guidance and to vote on a new Pope. It's a bit more complicated than that, but that's a very basic description.
Popes can not be fired. Popes are not generally related to each other (In theory, the Cardinals could select a Pope who is related to a previous Pope, but usually they are not. In fact, the last three Popes have all been from different countries from each other. Pope John-Paul II was from Poland [He passed away while Pope], Pope Benedict XVI was from Austria [He's still alive, but resigned], and Pope Francis is from Argentina).
Catholics believe that there have been 266 Bishops of Rome (Who eventually began to be referred to as Popes), beginning with St. Peter the Apostle in 33AD. Secular historians back up that lineage, except that they can't find evidence for or against St. Peter coming to Rome near the end of his life- but they basically can confirm everyone from the second guy in the list onward.
Here's Pope Francis's (now gloriously reigning in Rome) job description.
Thanks, Tad.
For anyone who doesn't recognize Tad's quote, it's from the bible. It's repeated in a couple of places, but I think Matthew 16:18-19 might be the one that best gets across the point being made in thread:
18 And I tell you, you are Peter, and on this rock, I will build my church, and the gates of Hades will not prevail against it. 19 I will give you the keys of the kingdom of heaven, and whatever you bind on earth will be bound in heaven, and whatever you loose on earth will be loosed in heaven.” (NRSV)