What are heresies? How did they threaten the church and how did the church fight them?

Heresy is a deliberate deviation from a certain interpretation of a religious teaching. It assumes a different approach to learning. Thus, a conflict arises between representatives of different teachings and the possibility of mutual accusation of heresy arises. The church had significant influence, had a lot of money. The heretics with their teachings undermined the authority of the church and its version of the teaching. If people have a choice, they will begin to hesitate and doubt the truthfulness and righteousness of the church. And this is a loss of power and money. The church could not allow this and created the Inquisition. It was a judicial body of the Church, which, through interrogation and torture, obtained the necessary testimony. Any dissenter was declared a heretic. If he did not give up his views, then a cruel death awaited him.