(a) temporary hell for Catholics.
(b) proof that the Church has a horrible, creeping fear that someone, somewhere is enjoying themselves.
(d) none of the above.
Right, it's none of the above. But then what is it?
The best explanation I've heard in a long time showed up in (of all places) Father Paul Scalia's funeral homily for his father, Supreme Court Justice Antonin Scalia. He never even uses the word "Purgatory."
Homily (it starts about 10 minutes in)
After hearing it, I finally get why Paul is asking for prayers for someone who's dead (2 Timothy 1:18). And why the Church cares about praying for the dead.
If we really love someone, we'll never stop praying for them.