They're just doors. They're part of the ceremony of kicking off the Catholic Holy Year of Jubilee every 25 years. The fifth door is new: it's a door in a prison, because Pope Francis cares a lot about prisoners, and the theme he's chosen is hope.
Tbh I'm not Christian but I find Pope Francis' focus on the plight of prisoners and forgiveness very interesting. He's by no means a perfect pontiff, but he seems very sincere about his principles there.
The other four, usual doors? The Holy Doors are sacred portals found within the four major Papal basilicas in Rome: St. Peter's Basilica, the Archbasilica of St. John Lateran, the Basilica of St. Mary Major, and the Basilica of St. Paul Outside the Walls.
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