Recommended Book: First Epistle of Clement to the Corinthians - Kindle Edition (get Kindle app for phone) (paid link)
Purgatory: The place and state in which souls suffer for a time after death and are cleansed of their sins, before entering into Heaven. Here, venial sins, which have never in this life been remitted by an act of repentance or love or by good deeds, are removed. The debt of temporal punishment due to grave sins, the guilt of which with its eternal punishment has indeed been remitted by God in the Sacrament of Penance or by perfect contrition, must also be removed since "nothing defiled shall enter heaven."
Council of Florence (1438-1443): "If they have died repentant for their sins and having love of God, but have not made satisfaction for things they have done or omitted by fruits worthy of penance, then their souls, after death, are cleansed by the punishment of Purgatory; also . . . the suffrages of the faithful still living are efficacious in bringing them relief from such punishment, namely the Sacrifice of the Mass, prayers and almsgiving and other works of piety which, in accordance with the designation of the Church, are customarily offered by the faithful for each other."