"Purgatory basically means that God can put the pieces back together again. That He can cleanse us in such a way that we are able to be with Him and can stand there in the fullness of life. Purgatory strips off from one person what is unbearable and from another the inability to bear certain things, so that in each of them a pure heart is revealed, and we can see that we all belong together in one enormous symphony of being."

--Pope Benedict XVI

--Saint Thomas Aquinas

We must empty purgatory with our prayers.

St. Pio of Pietrelcina

1030 All who die in God's grace and friendship, but still imperfectly purified, are indeed assured of their eternal salvation; but after death they undergo purification, so as to achieve the holiness necessary to enter the joy of heaven.

1031 The Church gives the name Purgatory to this final purification of the elect, which is entirely different from the punishment of the damned.  The Church formulated her doctrine of faith on Purgatory especially at the Councils of Florence and Trent. The tradition of the Church, by reference to certain texts of Scripture, speaks of a cleansing fire:

1031 The Church gives the name Purgatory to this final purification of the elect, which is entirely different from the punishment of the damned. The Church formulated her doctrine of faith on Purgatory especially at the Councils of Florence and Trent. The tradition of the Church, by reference to certain texts of Scripture, speaks of a cleansing fire: 

As for certain lesser faults, we must believe that, before the Final Judgment, there is a purifying fire. He who is truth says that whoever utters blasphemy against the Holy Spirit will be pardoned neither in this age nor in the age to come. From this sentence we understand that certain offenses can be forgiven in this age, but certain others in the age to come.

1472 To understand this doctrine and practice of the Church, it is necessary to understand that sin has a double consequence. Grave sin deprives us of communion with God and therefore makes us incapable of eternal life, the privation of which is called the "eternal punishment" of sin. On the other hand every sin, even venial, entails an unhealthy attachment to creatures, which must be purified either here on earth, or after death in the state called Purgatory. This purification frees one from what is called the "temporal punishment" of sin. These two punishments must not be conceived of as a kind of vengeance inflicted by God from without, but as following from the very nature of sin. A conversion which proceeds from a fervent charity can attain the complete purification of the sinner in such a way that no punishment would remain.

As Catholics we belong to one body of believers -- here on Earth (the Church Militant); in Heaven (the Church Triumphant) and in Purgatory (the Church Suffering).  The relationship among the three Communities that comprise the Body of Christ -- the Church -- is reciprocal:

The Church Triumphant in Heaven operates on a purely charitable basis:  Their prayers can assist us in the Church Militant on Earth, with nothing needed in return, except perhaps a willingness on our part to spread particular devotions to particular saints when prayers are answered.  

And we can certainly pray for ourselves, make sacrifices, and perform good works which increase our holiness, and thereby mitigate some portion of purification in Purgatory we would need otherwise.

But for the souls in Purgatory, they have only one disposition -- that of the recipient of our charity on earth, and the purifying fire of love from God in Heaven.  The souls in Purgatory cannot pray for themselves.  They are completely reliant on our intercession for them in order to hasten their arrival to Paradise. 

As such, you may have come across parishes that have something akin to a Purgatorial Society, whose sole mission is to pray for the departed.  Certainly the people of the parish are welcome to begin such a commendable work of mercy, but in its absence, each one of us can pray for our departed family members, our friends or spouses who've gone before us -- even complete strangers you may hear of in the news or on social media.  No prayer for the Church Suffering goes wasted.  Mass is offered every day for the deceased.  The Chaplet of Divine Mercy is uniquely powerful to recite in the 3 pm hour of the aftenoon -- the hour Christ expired on the Cross. 

And although the Poor Souls cannot pray for themselves, they can certainly pray for you.  Saint Augustine said it best: 



So the next time we attend a wake or a funeral - or just hear of someone's passing -- we would do well to remember that, although modern decorum overwhelmingly assumes a direct path to heaven at the moment of decease, our Catholic Faith teaches us infallibly that death is not the time to stop praying for the dearly departed, but exactly the time to increase our compassion for their souls by interceding for them, when they cannot intercede for themselves.  By doing so, we add to the purifying rays of God and win for the beloved souls their early release into heavenly bliss.