All Saints’ Day, All Hallows, or Hallowmas begins at Vespers on the evening of 31 October – which, of course, is known as the Eve of All Hallows, Halloweven or Hallowe’en, and ends at sundown on 1 November.
This is the feast commemorating the saints, all those who have attained the beatific vision in Heaven.
The following day, unless it is a Sunday, is called All Souls’ Day.
The Feast of All Souls is a day of prayer for all the Faithful departed who have not yet been purified in the fires of Purgatory and reached Heaven, remembering that there is a union of prayer between those in Heaven (the "Church triumphant"),those in Purgatory (the "Church suffering") and the living (the "Church militant").
The Church Suffering are taken from Purgatory into Heaven to join the Church Triumphant
Pope St Gregory III