On the first two days of November each year, the Church commemorates two linked feast days: All Saints (November 1) and All Souls (November 2). All Saints is easy to understand: We remember all those who have lived lives of heroic holiness, whether the Church has canonized them or not. On All Souls, we remember all those who have died, not just the spiritual superstars.
From the earliest days the church has prayed for the deceased. Their judgment is in the hands of God, and we trust in God’s mercy. But we also believe the God cares about us and our concerns, so prayers for our deceased loved ones are appropriate.
The feast day itself is rooted in the second century. In the 10th century, St. Odilo of Cliny established a memorial of all the faithful departed. Rome added the feast to the church’s calendar in the 13th century. In many parts of the world the celebration of this feast day is marked with particular energy, such as el Dia del los Muertos in Mexico.
It’s appropriate to commemorate All Souls Day by praying for those who have gone before us in faith. Some people also visit the graves of their loved ones to pray for them.
The feast of All Souls reminds us of our mortality. We are all finite, mortal creatures. We are all loved by God, who has endowed us with an immortal soul. Our ultimate destiny lies in God’s hands, and even death does not separate us from his love.
(taken from http://www.foryourmarriage.org/two-great-feasts-all-saints-and-all-souls)