Sanfedismo was a movement that happened in Italy a long time ago (around 1799) when people were trying to figure out how to run their country.
Imagine you and all your friends are trying to make a really big puzzle together, but you all have your own ideas on how to put it together. Some want to start with the corners, while others think it's best to start in the middle. This kind of confusion is what was happening in Italy during that time.
Some people thought that the best way to run Italy was to support the Pope (who was basically the leader of the Catholic Church and a big deal in Italy). These people are called Sanfedisti. They believed that if everyone followed the teachings of the Pope then Italy would be a great place to live.
Other people thought that Italy could only be great if everyone was equal and had the same rights. They didn't believe in the Pope having so much power. These people were called Jacobins.
The Sanfedisti and the Jacobins didn't get along very well, so there was a lot of fighting and disagreements. The Sanfedisti were eventually able to defeat the Jacobins and take control of Italy for a little while.
So basically, Sanfedismo was a movement that believed in supporting the Pope, while the Jacobins believed in equality and didn't like the Pope having so much power. They fought a lot and the Sanfedisti ended up winning.