God wants everyone to be able to go to heaven. Jesus instituted the Sacrament of Reconciliation (confession) so that we can receive forgiveness of our sins after Baptism. To be totally without (remnants of) sin upon arrival in heaven with God, these have to be expiated in purgatory.
Sometimes the pope can grant an indulgence to reduce the time spent in purgatory. This indulgence is a sign of God’s mercy and can be obtained, for example, by praying a certain prayer or by making a pilgrimage. In essence, therefore, indulgences are something beautiful. In the Middle Ages, however, indulgences were crudely abused and sold as “tickets to heaven”. Criticism of this practice is entirely justified.
