Happy are those who have died in the Lord.
Let them rest from their labors for their good deeds go with them. —Rev 14:13
31 October and 1 and 2 November are called, colloquially (not officially), "Hallowtide" or the "Days of the Dead" because on these days we pray for or remember those who've left this world.
The days of the dead center around All Saints Day (also known as All Hallows) on November 1, when we celebrate all the Saints in Heaven. On the day after All Hallows, we remember the saved souls who are in Purgatory being cleansed of the temporal effects of their sins before they can enter Heaven. The day that comes before All Hallows, though, is one on which we unofficially remember the damned and the reality of Hell. The schema, then, for the Days of the Dead looks like this:
|Hallowe'en:||unofficially recalls the souls of the damned. Practices center around the reality of Hell and how to avoid it.|
|All Saints:||set aside to officially honor the Church Triumphant. Practices center around recalling our great Saints, including those whose names are unknown to us and, so, are not canonized|
|All Souls:||set aside officially to pray for the Church Suffering (the souls in Purgatory). Practices center around praying for the souls in Purgatory, especially our loved ones|
As Catholics, we say we celebrate All Saints and All Souls Day. In the early days of November, we recall to mind our beloved dead with beautiful Masses and customs worldwide in their honor. St. John, the beloved disciple, reminds us:
The Vigil of All Hallows ("Hallows Eve," or "Hallowe'en") came, in Irish popular piety, to be a day of remembering the dead who are neither in Purgatory or Heaven, but are damned, and these customs spread to many parts of the world. Thus we have the popular focus of Hallowe'en as the reality of Hell, hence its scary character and focus on evil and how to avoid it, the sad fate of the souls of the damned, etc.
How, or even whether, to celebrate Hallowe'en is a controversial topic in traditional circles. One hears too often that "Hallowe'en is a pagan holiday" -- an impossibility because "Hallowe'en," as said, means "All Hallows Evening" which is as Catholic a holiday as one can get. Some say that the holiday actually stems from Samhain, a pagan Celtic celebration, or is Satanic, but this isn't true, either, any more than Christmas "stems from" the Druids' Yule, though popular customs that predated the Church may be involved in our celebrations (it is rather amusing that October 31 is also "Reformation Day" in Protestant circles -- the day to recall Luther's having nailed his 95 Theses to Wittenberg's cathedral door -- but Protestants who reject "Hallowe'en" because pagans used to do things on October 31 don't object to commemorating that event on this day).
One hears that the Vigil used to be a day of fasting in the Church so Catholics should treat the day as penitential. It is true, that the day used to be a day of fasting, but it was not so and is not so according to the laws in place in 1962.
All Souls has its origins in A.D. 1048 when the Bishop of Cluny decreed that the Benedictines of Cluny pray for the souls in Purgatory on this day. The practice spread until Pope Sylvester II recommended it for the entire Latin Church.
The need and duty of prayer for departed souls has been promulgated by the Church at all times. Catholics believe in a supernatural solidarity with the deceased through the Communion of Saints, and of their need for further purification after death. It is an ancient Catholic custom to pray for and give alms in the name of our beloved dead especially at this time of year.