The correct terminology is "the selling of Indulgences".
An "Indulgence" is a document that the Catholic church can grant to a person to remove the temporal punishment for a specific sin. It does not in itself forgive the sin, that is a separate issue.
At the time of Martin Luther, the Pope (Leo X) was in the middle of the reconstruction St. Peter's Basilica, a task that the church did not have enough money to pay for. So the Pope offered to grant Indulgences for any desired sin to those who would donate to this construction project.
Many of the individuals assigned the task of traveling the countryside to collect such donations were less than honest and often misrepresented the Indulgence as actually forgiving a sin before it was committed and instead of simply accepting a voluntary donation misrepresented the transaction as a sale (some even kept large percentages of the money collected for themselves).
This practice of selling of Indulgences was just one of the 95 complaints against the Catholic Church of the time raised by Martin Luther, and it was one of the man reasons the Pope excommunicated him as it threatened funding of the Pope's present and future reconstruction plans in Rome.
BTW, i agree completely with the Expert answer by James Hough given above: The Catholic Church has never sold indulgences, ever. It was the misrepresentations by a few of those tasked to collect the donations that the indulgences were being sold and what they did for you that Martin Luther complained about, wanted discussed, and wanted corrected. However instead of considering Martin Luther's complaints for the possibility of validity, the Pope just excommunicated him.
Pope Leo X was accused by Martin Luther of selling indulgences or allowing the sale of indulgences.
They stopped selling indulgences.
Martin Luther
Selling indulgences raised money for the church and the pope. They managed to convince the people to buy indulgences even though common sense would tell people that buying a piece of paper does not rid all of a person's sins.
no it wasn't the primary cause for the Enlightment
Luther protested the practice of selling indulgences. what was that practice?
Luther protested the practice of selling indulgences. what was that practice?
There were many clerics of all ranks selling indulgences.
Luther protested the practice of selling indulgences. what was that practice?
Pope Leo X was accussed by Martin Luther of selling indulgences.
the selling of pardons for your confessions inexchange for lucre for the priest
Pope Leo X was accused by Martin Luther of selling indulgences or allowing the sale of indulgences.
Selling indulgences for money.
Luther protested the practice of selling indulgences. what was that practice?
They stopped selling indulgences.
Martin Luther
Selling indulgences raised money for the church and the pope. They managed to convince the people to buy indulgences even though common sense would tell people that buying a piece of paper does not rid all of a person's sins.