The Pope would charge for anything. Even as simple as Communion.
The Pope would say that paying him, that whomever they payed for would have less sins to work off. People would donate so much, they could barley support their families.
The Pope would go against their own teachings, such as drinking.
Someone named Martian Luther noticed these things, and made a list of the things that the Pope was doing wrong called "Notes of Indulgence," and thanks to the printing press, people were able to read it. He put it on Catholic church doors for people to read.