Short answers, pulled from the story.
The word purgatory emerged as a noun between 1160 and 1180 to describe a physical location rather than a spiritual process. Before this period, early Christians spoke of a cleansing fire or an intermediate state without conceptualizing it as a distinct third place between heaven and hell.
The publication of the Tractatus de Purgatorio Sancti Patricii played a decisive role in fixing the concept in the public imagination. This narrative described a knight's journey through a cave on Station Island in Lough Derg, Ireland, turning an abstract theological notion into a tangible geography of the afterlife.
The Second Council of Lyon met in 1274 to officially define the teaching of purgatory. By this time, the popular image of a fiery place had already taken root in the minds of the faithful, driven by the vivid imagery of medieval literature and art.
St. Catherine of Genoa described purgatory as a state of both joy and voluntary pain in the early sixteenth century. She reframed the fire as an internal, voluntary, and loving process of purification that is ultimately joyful.
The Council of Trent met in 1563 to warn against speculating on difficult and subtle questions regarding purgatory. Modern popes like John Paul II and Benedict XVI have clarified that the term refers to a condition of existence rather than a place.
The Protestant Reformation of the sixteenth century marked a decisive break with the Catholic doctrine of purgatory. Martin Luther explicitly rejected the idea, and the Thirty-Nine Articles of the Church of England, written in the 1560s, condemned the Romish doctrine of purgatory as vainly invented.