Catechism of the Catholic Church
c. Para. 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.
Para. 1031: The Church gives the name Purgatory to this final purification of the elect, which is entirely different from the punishment of the damned (Cf. Council of Florence [1439]: DS 1304; Council of Trent [1563]: DS 1820; [1547]: 1580; see also Benedict XII, Benedictus Deus [1336]: DS 1000).