All Souls Day is celebrated by the Roman Catholic Church on the day after All Saints Day. Historically it has been viewed as remembering the faithful departed who yet have time to serve in Purgatory, and are on their way to future heavenly blessedness. Observance tends to focus on family members. In Anglican churches, it is an extension of All Saints Day, merely remembering the faithful departed.
you are the glory of believers
and the life of the just.
Your son redeemed us
by dying and rising to life again.
Since our departed brothers and sisters
believed in the mystery of our resurrection,
let them share the joys and blessings
of the life to come.
(You can find this prayer in the context of “The Office for the Dead” here).