Anti-Popes: Is the Chair of Peter Empty? Can We Have a Heretical Pope?

What is an Anti-Pope? Are they evil or Satanic? Or are they just men who claim they are the rightful Pope. And how does the Church determine the real Pope? Many claim the Chair of Peter is empty and the last two Popes are heretical. Can this be possible? And if so, how? Join Fr. Chris Alar as he explains this and more!