Purgatory is not mentioned anywhere in the Bible, and in fact, the word did not come into common parlance until the 12th century. However, the concept of a process whereby souls are purified before they enter heaven was evident in very early Christianity. Going back even further, there is a Jewish tradition that praying for the dead furthers the purification of a soul(s). Although sometimes Purgatory is imagined as a physical place, the Catholic teaching is that Purgatory is the “final purification of the elect.” The Catechism of the Church describes it this way;
“All who die in God’s grace and friendship, but still imperfectly purified, are indeed assure of their eternal salvation; but after death they undergo purification, so a to achieve the holiness necessary to enter the joy of heaven.” (CCC 1030)