Of course this is true; and God uses the church He founded on Peter, (Mathew 16:18), to accomplish the task.
Purgatory is where those already saved reside, until they are purged from any minor sin they died with.
The existence of purgatory was universally taught by all the Fathers of the Church. The words of Our Lord, taught in parable form, "You shall not come out from it until you have paid the last penny" are very clear. (Matt. 5:25-26).
There are serious sins that can condemn us to Hell, and lesser ones that do not, as St. John the Evangelist teaches us: "He that knows his brother to sin a sin which is not to death, let him ask, and life shall be given to him, who sinneth not to death.---and there is a sin unto death." (1 John, 5:16-17).
Yet, all sin, even minor sin we die with, must be punished, for "nothing unclean can enter (heaven)", (Revelation 21:27).
Jesus reveals that sins against the Holy Spirit cannot be forgiven in this world, "or in the next"; implying that some sins can be forgiven in the next world: "And whoever says a word against the Son of man will be forgiven; but whoever speaks against the Holy Spirit will not be forgiven, either in this world or in the next.". (Mathew 12:32)
Paul also shows his belief in purgatory when, in his second letter to Timothy, he prays for the deceased Onesiphorus. "May the Lord grant him to find mercy from the Lord on that day" (2 Tim. 1:18).
"If any mans work is burned up, he will suffer loss, though he himself will be saved, but only as through fire". (I Corinthians 3:15)
"For if he were not expecting that those who had fallen would rise again, it would have been superfluous and foolish to pray for the dead. But if he was looking to the splendid reward that is laid up for those who fall asleep in godliness, it was a holy and pious thought. Therefore he made atonement for the dead, that they might be delivered from their sin." (2 Maccabees 12: 44-45)
NOTE: The two books of Maccabees, called the "Apocrypha" by Protestants, but held as canonical Scripture by the Catholic Church since 400 A.D., can be used to prove the doctrine of Purgatory even though Protestants and Fundamentalists reject it as inspired Scripture. This is so because all mainstream Christian denominations and Scripture scholars do accept these books as accurate historical accounts of Old Testament Jewish faith. Thus, they are included in most Protestant Bibles as "Apocrypha" because they are regognized for their excellent historical value, even though rejected as inspired verses. Hence, we know from the ancient historical accounts of 2 Maccabees that the Old Testament Jews did believe in Purgatory, or a place of rest between Heaven and earth where prayers can be effective to their salvation.
pax Christi