All Souls Day, Pray for the dead, November 2.
All Souls Day is a holy day set aside for honoring the dead. According to Catholic belief, the soul of a person who dies can go to one of three places. The first is heaven, where a person who dies in a state of perfect grace and communion with God goes. The second is hell, where those who die in a state of mortal sin are naturally condemned by their choice. The intermediate option is purgatory, which is thought to be where most people, free of mortal sin, but still in a state of lesser (venial) sin, must go.
Consistent with these teachings and traditions, Catholics believe that through the prayers of the faithful on Earth, the dead are cleansed of their sins so they may enter into heaven.