What happens to the leadership of the Catholic Church when a pope becomes sick or incapacitated?

What happens when a pope is incapacitated? Is he still pope? Pope Francis remains hospitalized in critical condition with a complex lung infection. But he is still pope and very much in charge. His age and prolonged illness, though, have raised questions about whether he might resign, and revived interest about how papal power is exercised in the Holy See, how it is transferred and under what circumstances. Here’s how it works.