Through the passage of time, this feast lost its pagan religious roots and became the costumed celebration it is today. Pumpkins have replaced turnips. Treats are given to kids and not ghosts.
The Church Christianized this feast of the dead in the 9th century, just as the pagan feast of the saturnalia was Christianized as the celebration of Christmas from December 25 through January 6. This was a way of helping the Christians who spread so rapidly to pray and to understand and celebrate the faith. So, on November 1 we have All Saints Day. The night before was called All Hallows Eve, whose contraction is Hallowe'en. The purpose was and is honoring the Saints: those faithful departed who are in Heaven beholding God face to face (the Beatific Vision). The Halloween tradition is harmless unless it is used not for fun, but to glorify evil.
This Saturday is November 1 when we commemorate the victory of our brothers and sisters in Heaven. We recognize not just the popular Saints like St. Simon and St. Jude whose feast day is October 28. But we also honor those who led ordinary lives on earth, living according to faith. Many of them are our own relatives. We ask them and all the Saints to be our prayer partners so that we may join them in Heaven one day.