So, a long time ago in a place called Italy, there was a man named Francis. He really loved animals and nature and wanted to help people too. One day, while he was praying in a little chapel, he heard a voice that asked him to "rebuild my church". At first, he thought it meant to actually fix the broken-down chapel he was in, but then he realized it meant something much bigger - to help people find faith in God again.
He started doing all sorts of good things for people, like giving away his own clothes to those who didn't have any, and even preaching about God to people on the streets. People started following him and helping him, and they became known as the Franciscans.
One time, there was a man who was very sick and had leprosy. Back then, people with leprosy were not allowed to be around others because it was thought to be very contagious. People were scared of them and didn't want to be near them. But Francis didn't care. He went right up to the man and hugged him, and even kissed his hand. He wanted to show that everyone deserves love and kindness, no matter what.
The Pope at the time was called Pope Innocent III, and he liked what Francis was doing. He even gave him permission to form a new religious order that focused on helping the poor and preaching about God. This was a big deal, because before that only people who lived in monasteries could form religious orders.
Decades later, after Francis had died, another Pope wanted to remember him and everything he had done. So, he declared a "Pardon of Assisi". This meant that if people visited the church in Assisi, where Francis was buried, during a special time, they would receive a special blessing from God. It was like a way of saying thank you to Francis and encouraging people to follow in his footsteps of helping others and being kind.
So, that's basically what the Pardon of Assisi is. It's a way of remembering a really great person who did amazing things for others and reminding ourselves to be kind and helpful too.