The Church observes the month of November as the month of the saved souls in purgatory. The souls in Purgatory are considered as the 'suffering church'. The righteous souls (saints) who have fought a good war and completed the mission assigned by their Master in this world are known as the 'victorious Church' and the ones still living on this earth including you and me are the living Church. While the Church believes that the glorious ones (Saints) are glorifying and thanking the Creator and Savior unceasingly and interceding for the salvation of the living Church (the whole humanity), the suffering souls in the purgatory depend fully on the prayers of the faithful - as they cannot do anything for themselves as long as they are in that state.
So it is our duty and highly expected by our Savior, to pray and offer Sacraments for those souls as the Good Lord who is the peak of Mercy (also Justice) can show kindness to them against the intercessory prayers offered by the living Church. In return once they are elevated, they in turn intercede for the mankind.
It is very imperative for a devotee to remember his/her departed parents / grand parents /uncles /aunts / teachers /Priests / nuns / neighbors / friends / colleagues / .... every known souls throughout his/her life and pray for those souls, it is highly recommended to pray specially for those souls in the month of November without fail. All what one can do for a departed soul is offering prayer, penance and Sacraments. And no doubt the result will be highly rewarding.